Css
References
- Specification
- W3Schools
- CSS Reference from W3Schools
- CSS Tutorial from W3Schools
Syntax
External CSS
External CSS is a file that contains only CSS code and is saved with a .css file extension. This CSS file is then referenced in your HTML using the <link> instead of <style>.
Content of file test.css:
body{ background-color: gray;}
p { color: blue; }
h3{ color: white; }
Example html file using the stylesheet above:
<html>
<head>
<link rel="stylesheet" type="text/css" href="test.css" />
</head>
<body>
<h3> A White Header </h3>
<p> This paragraph has a blue font.
The background color of this page is gray because we changed it with CSS! </p>
</body>
</html>
Internal CSS
When using internal CSS, you must add a new tag, <style>, inside the <head> tag.
<html>
<head>
<style type="text/css">
p {color: white; }
body {background-color: black; }
</style>
</head>
<body>
<p>White text on a black background!</p>
</body>
</html>
Inline CSS
To add style to a given HTML element, just specify the desired CSS properties with the HTML style attribute:
<p style="background: blue; color: white;">A new background and font color with inline CSS</p>
Selectors
See the reference here.
| Pattern | Meaning | Described in section |
|---|---|---|
*
|
Matches any element. | Universal selector |
E
|
Matches any E element (i.e., an element of type E). | Type selectors |
E F
|
Matches any F element that is a descendant of an E element. | Descendant selectors |
E > F
|
Matches any F element that is a child of an element E. | Child selectors |
E:first-child
|
Matches element E when E is the first child of its parent. | The :first-child pseudo-class |
E:link E:visited
|
Matches element E if E is the source anchor of a hyperlink of which the target is not yet visited (:link) or already visited (:visited). | The link pseudo-classes |
E:active E:hover E:focus
|
Matches E during certain user actions. | The dynamic pseudo-classes |
E + F
|
Matches any F element immediately preceded by a sibling element E. | Adjacent selectors |
E[foo] E[foo="warning"] E[foo~="warning"]
|
Matches any E element whose "foo" attribute set OR value is exactly equal to "warning" OR value is a list of space-separated values, one of which is exactly equal to "warning". | Attribute selectors |
DIV.warning
|
Language specific. (In HTML, the same as DIV[class~="warning"].) | Class selectors |
E#myid
|
Matches any E element with ID equal to "myid". | ID selectors |
Miscellaneous
Using Opera DragonFly
Opera DragonFly is a powerful tool to write / debug CSS:
- Browse rapidly and easily through all CSS properties of any visual object, and get detailed view on how they are computed.
- Easy access to CSS property documentation.
Font size
- Use property
font-sizeto define the font size of a given visual element.
Short reminder on font sizes:
- pt (points) is defined as 1/72 of screen inch. For 96 dpi resolution (i.e. 96 pixels per inch), we have 1pt=1.333px.
- px (pixel) the smallest graphic element on the screen. The number of pixels (or dots) per inch (DPI) gives the screen resolution. Nowadays DPI is usually equal to 96.
- em (for the letter M) is a unit of width in the field of typography, equal to the currently specified point size. Originally 1em was the width of the capital M in the current font.
Some usual values (see also pxtoem.com):
| DPI | 1 pt | 12pt (1 pica) |
|---|---|---|
| 72 | 1px | 12px |
| 96 | 1.333px | 16px |
Note that em is a relative font size. It sets the size of current elements in function of the size of the containing parent. So 1.2em means 20% current font size of parent object.
.
Examples
/* install_log class for install log table */
table.install_log td:first-child
{
width:7.5em;
font-size: x-small;
}
table.install_log td:first-child:before
{
content:url(/miki/skins/monobook/bullet.gif);
margin-right:0.6em;
}