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CSS cheat sheet

While reading CSS books and experimenting I found it helpful to take notes and put together a cheat sheet for quick reference. I figured others might find it useful so I'm sharing. I've also uploaded a simple PDF version.

Selectors

Basic

h1
    select all <h1> tags
h1.special
    select h1 tags of the special class
h1#special
    select h1 tags of special id

p a
    select <a> tags descendant from p

h1, h2
    select both h1, h2

*
    select all tags
    implicit in
        .class = *.class
        #class = *#class

#banner *
    select all tags inside banner

a:link
    selects link that guest hasn't visited
    regular style

a:visited
    link that visitor has clicked before

a:hover
    link when mouse is hovered over

a:active
    link when it's clicked (just a ms)

.class1.class2
    select elements that have both class1 and class2

Pseudo-classes

generate content
    :before
        inserts content before
        p.tip:before {content: "HOT TIP!" }

    :after
        like :before but after

    properties
        generated pseudo-classes can be styled like any other
            display
            color
            border

        content
            string
                content: "(link) "

            urls
                content: url(path/to/image)

            attributes
                content: attr(href)

            combinations
                content: " [" attr(href) "]"

:first-child
    select and format just the first child of an element

    e.g.,
        li:first-child { font-weight: bold; }
            formats all first elements in bold

:focus
    when element receives focus (e.g., click or tab)
    e.g.,
        input:focus { background-color: #FFFFCC; }

Advanced selectors

child selectors
    body > h1
        select any h1 that is a child of body

adjacent siblings
    h2 + p
        select p right after h2

attribute selectos
    img[title]
        select only img tags with "title" attribute

    .photo[title]
        select any element with photo class and a title attribute

    input[type="text"]
        input fields of type text

    a[href][title]
        select a that has both href and title attrs

    *[title]
        any element that has title attribute

    img[title~="Figure"]
        any img with title that contains Figure in it
            regexp match?

    img[title^="bar"]
        any img with title that starts with "bar"

    img[title$="bar"]
        any img with title that ends with "bar"

    img[title*="bar"]
        any img with title that contains substring "bar"

    *[lang|="en"]
        any element with lang attr that
            equals en
            begins with en-

Pseudo-classes

:first-line
:first-letter
    just the first letter

can only be applied to block elements (not inline)

Psuedo-elements

:before
:after

# examples

h2:before {content: "]]"; color: silver;}
body:after {content: "  The End.";}

Floats

containing block
    nearest block-level ancestor

floated element generates a block box
    regardless of its type
    will be laid out as a float

Rules

  1. stay within borders of containing element

    left/right outer edge may not be to the left of inner left/right containing block.

  2. give precedence to existing floats

    prevent floats from overwriting each other

    floats are safe

    left outer edge must be to the right of the right outer edge of a preceding element.

  3. no overlapping between float elements

    if they collide the loosing element will be floated down

  4. can't be higher than inner top (pre-padding) of containing parent

  5. floats can't be higher than the tops of preceding floats

    If we have 3 floats, and the first two are floated to the left, the third float will float only as high as the second float.

  6. floats can't float higher than the top of the line box generated by a preceding element

  7. floats get pushed down to a new line height if there isn't room for them in the containing box

  8. given the above constraints, float as high as possible

  9. left floating elements try to float as left as possible, right floating elements try to float as right as possible

    BUT

    a higher position is preferred to floating more right

Rule consequences

when floated element is taller than container?
    the bottom sticks out of the container

    countermeasure
        floated element will expand to contain floated
        descendants

negative margins
    can cause floats to appear to escape their parents

    just like negative margins on non-floated elements
        can make the child appear wider than it's parent

if floated element is wider than it's parent
    it can stick out

negative margins may cause a float to overlap inline elements
    inline elements rendered on top of the float

a float expands to contain anything in it

move to the left or right edge of the
    browser window (or containing window)

floated inline methods are treated like blocks

content with a background or border runs underneath the float
    how to prevent this - overflow: hidden

clear property
    don't wrap around a floated item
    left - drop below left floated items
    right - drop below right floated items
    both - drop below both

Positioning

position := static | relative | absolute | fixed | inherit

    static
        generated as normal

    relative
        offset by some distance
        element retains it's shape
        space it would ordinarily have occupied preserved

    absolute
        removed from the flow

        positioned with respect to its *containing* block
            may be another element in the document

        space the element might have occupied is closed up
            as if the element didn't exist

        positioned element generates a block-level box
            even if it's inline

        fixed
            element box behaves like absolute
                but containing block is the viewport itself

containing block

    in HTML the root element is HTML
        some browsers use body
        initial containing block
            rectangle the size of the viewport

    nearest ancestor (of any kind) that has position value != static
        block-level containing ancestor
            padding edge (I.e., border bounded area)

        inline-level containing ancestor
            content edge of the ancestor
                in ltr lang - top left corner, right bottom corner

        no ancestors?
            initial containing block

    important - elements can be positioned outside containing block
        maybe it should be called "positioning context" instead

offset properties

    top, right, bottom, left := <length> | <percentage> | auto | inherit

        percentage
            containing width for left / right
            height for top / bottom

        auto
            element position if it were static

    positioning can cause height/width to be calculated automatically
        e.g.,
            height 100%
                top: 0
                bottom: 0

            width 100%
                left: 0
                right: 0

    margins apply to the position boundaries
        you're really specifying the position of the outer edge

    setting width/height can make a difference
        IF you set borders, padding, margin
        because width/height set inner edges
            the content box

fixed position
    can be used to simulate frames of old
    just like absolute position except
        the containing block is the viewport

Properties

formatting text
    line-height
    letter-spacing # how much space to add between letters

    font-family
        sans # clean and simple appearance (for headlines)

            Arial
            Helvetica
            Verdana
            Tahoma
            Formata
            Sans

        serif # better for long passages of text
            Georgia
            Times
            Times New Roman

        popular combinations
            Arial, Helvetica, sans-serif
            "Times New Roman", Times, serif
            "Courier New", Courier, monospace
            Georgia, "Times New Roman", Times, serif

    font size
        keywords
            xx-small x-small small medium large x-large xx-large

            each increase or decreases by 1.2

        ems and percentages the same thing

    font styles
        font-style: italic|bold|normal
        text-transform: uppercase
        font-variant: small-caps

        text-decoration: underline|overline|line-through|blink

    spacing attributed
        letter-spacing
        word-spacing
        line-height
            normal setting is 120%

    alignment
        text-align: left|center|right|justify

    text-indent

        e.g., text-indent: 3em
            indent first line 3em

    text-shadow
        <color> <offset-x> <offset-y> <blur-radius>?

    text-shadow: green 5px 0.5em;
        not supported in Firefox

    white-space
        normal | nowrap | pre | pre-wrap | pre-line | inherit

            normal := discards extra whitespace
                collapses multiple "spaces"

            pre := treated as if it's pre
                whitespace is nog ignored

                pre-line := whitespace collapsed, linefeeds honored

                pre-wrap :=
                    like pre except lines wrap

            no-wrap := prevent wrap breaks from being rendered
                line breaks must be inserted with <br />

lists
    list-style-type: square|disc|circle
    list-style-position: outside|inside

margins and padding
    margin: 5px
        5px on all sides
    margin: 5px 1px
        5px top and bottom
        1px on the sides

    margins between elements don't get added
        the larger of the two margins is applied

    padding is added

    whenever vertical margins touch the margins collapse


inline vs block
    display: inline|block;

    inline elements don't get any taller with padding or margins

    except for img tags

colors
    rgb(30%, 30%, 30%)
    #FFF #FFFFFF

    names
        aqua
        fuchsia
        lime
        olive
        red
        white
        black
        gray
        maroon
        orange
        silver
        yellow
        blue
        green
        navy
        purple
        teal

border
    each side can have a different property

width / height
    em is the text size
    percentages = size of containing element

    max-width
    min-width

    max-height
    min-height

    width/height do not include borders, padding and margins
        just the content

    displayed width = width + left padding + right padding + left border
    + right border + left margin + right margins

height property
    dangerous because it's hard to know in advance the size of content
    in a box

amount of margins between paragraphs, headlines
    varies from browser to browser
    for consistent predictable results set this yourself

background images

    background-image: url(images/bg.gif);
        url is relative to the stylesheet not the HTML page
        root relative
        absolute

    background-repeat
        repeat
            normal setting, repeat both on x and y

        repeat-x

        repeat-y

        no-repeat
            displays the image a single time

        background-position
            precise values
                <distance-from-left> <distance-from-top>

            keywords
                <horizontal> <vertical>
                    <horizontal> := left|center|right
                    <vertical> := top|center|bottom
                        bottom is the bottom of the content
                            not necessarily the bottom of the pag

                e.g.,
                    background-position: left center

            percentages

    short hand
        background := <background-color> <background-image>
        <background-attachment> <background-position>

    it's possible to replace borders with hand-drawn lines

overflow := hidden | visible | scroll | auto
    visible - normal setting what browsers usually do
    scroll - add scroll bars
    auto - make scroll bars optional
    hidden - hides extended content
        clipping can provide precise control over hidden content overflows

visibility := visible | hidden | collapse | inherit

    in invisible state the element is still there
        you just can't see it
        it effects layout normally

    descendant of invisible element can be visible

Outlines

Like borders except:

  • they don't cause reflow: good for adding an outline to emphasize focus
  • they can be non-rectangular
  • they can invert the background

Syntax:

outline := <outline-color> || <outline-style> || <outline-width>

outline-width := thin | medium | thick | <length>
    only one (unlike borders with top bottom left right)
outline-style := dotted | dashed | solid | double | groove |ridge | inset | outset

outline-color := <color> | invert | inherit

Tips

separation of concerns
    HTML should describe structure
        don't use class names that describe style

    CSS should describe styling

start with an inline style sheet
    after perfection move CSS code to an external sheet

title attribute adds tooltips to images and links

don't use div when you can use HTML tags

classes vs ids
    classes for repeating elements
    id selectors for unique elements

    ids get priority

margin: 0 auto
    lets content float
    equivalent to <center>

margins collapse

line-height creates implicit padding

Workflow

put temporary code on top of the stylesheet
    makes it easiest to work with firebug

name classes by structure, not styling
    separation of concerns
        HTML for content structure
        CSS for styling

refactor
    eliminate code
        CSS
        HTML
        let the future take care of itself

    use advanced selectors (instead of tons of classes)
    use more tag types when available
        not everything should be a div

minimize reloads
    edit CSS mode
        better than editing on server

    copy to server at the end

    refactor in gvim

debugging
    draw borders to better understand box model

use two firebug windows
    one for selecting
    one for editing live

Misc

element types
    replaced vs non-replaced

        whether or not the content is included in the HTML
            most html tags non-replaced
            replaced tags
                img
                input tag

    block vs inline
        block
            by default
                fills its parent element
                can not have other elements at its sides
                    I.e., generates a break before and after box

                e.g.,
                    p
                    div
                    li
                        special case that generates marker

        inline
            generated line boxes that are flowed within parent

internal style sheet
    <style type="text/css"></style>
        only in the head

    inline style sheets
        no time and bandwidth saving

class names
    letters, numbers, hyphens and underscores
    must start with a letter
    case sensitive

terminology
    ancestor
    descendent
    parent
        closest ancestor
    child
        closest descendent
    siblings

inheritance
    not passed
        border properties
        placement properties
            margins
            paddings

Specificity of CSS properties

    highest specificity wins

    weights
        tag selector = 1
        class selector = 10
        ID selector = 100
        inline style = 1000

    overruling specifiy
        !important after any prperty

        a { color: teal !important; }

organizing styles and stylesheets
    name styles by purpose not appearance
    refactor common styles to separate classes
        combine multiple classes

    group styles
        apply to related parts ofa page
        group styles with related purpose

xhtml
    differences from HTML
        lowercase tags
        quotation marks required for xhtml
        all tags must be closed
            <br />

    validator.w3.org

    tags
        p # for paragraphs
        li
        dl # definition list
        dt # definition term
        blockquote # quotes
        q # one line quotes
        cite # referencing
        address # identify and supply contact info

    table
        tags
            caption
                attribute align=top|bottom
            colgroup
                col
            thead
                tr
                    th
            tbody
                tr
                    td

        cell properties
            text-align
            vertical-align top|baseline|middle|bottom

        border-collapse: collapse|separate
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Comments

vertical-align

vertical-align top|baseline|middle|bottom

Confusing cheat sheet

I appreciate you showing your CSS cheat sheet online, but honestly, some of the stuff are hard to understand (such as positioning), maybe only you can understand (that's why it's a cheat sheet for *you*).

sasha grey

Couldn't agree more. I totally don't understand some code verse. An explaination is nessary.

I think its possible.

I think its possible. Creating frame and layout with CSS 4 is not that hard.

Clipping Path

perfect list

i need all this stuff as a web designer, i mostly use background-position, i use just one picture and direct it with background position, thats really useful cauz it request just one picture and page loads fast, thank you

When I initially commented I

When I initially commented I clicked the \”Notify me when new comments are added\” checkbox and now each time a comment is added I get several emails with the same comment. Is there any way you can remove people from that service? Cheers!

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