Liens externes sur feuilles de style

W3C, CSS Current Work. [Avancement des travaux sur CSS Level 3.]
W3C, CSS 2.1, Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification. [Table des matières.]
W3C, CSS 2.1, Introduction to CSS 2.1

Intégration de la feuille de style dans le document. Définition des règles sous l'élément STYLE qui vient se positionner comme élément fils de l'élément HEAD, après l'élément TITLE.

Externalisation de la feuille de style. Définition des règles dans la feuille de style ; l'intégration est assurée par l'élément LINK qui vient se positionner comme élément fils de l'élément HEAD, après l'élément TITLE.

Introduction des mécanismes d'héritage et de surcharge.

Distinction entre grandeurs -- ou unités -- absolues et relatives.

W3C, CSS 2.1, Syntax and basic data types

[Extraits de la spécification sur règles, blocs de déclaration et sélecteurs.

A rule set (also called "rule") consists of a selector followed by a declaration block.

A declaration block starts with a left curly brace ({) and ends with the matching right curly brace (}).

In between there must be a list of zero or more semicolon-separated (;) declarations.

A selector always goes together with a declaration block.]

[Extraits sur codage des propriétés et intégration des URLs.

A declaration consists of a property name, followed by a colon (:), followed by a property value.

The format of a URI value is 'url(' followed [...] by the URI, followed by ')'.]

[Extraits sur codage des couleurs.

<color> is either a keyword or a numerical RGB specification.

The list of color keywords is: aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, orange, purple, red, silver, teal, white, and yellow.

The format of an RGB value in hexadecimal notation is a '#' immediately followed by either three or six hexadecimal characters.]

W3C, CSS 2.1, Lengths. [Unités de longueur absolues vs relatives et pixel vs reference pixel.]

" The format of a length value is a number (with or without a decimal point) immediately followed by a unit identifier (e.g., px, em, etc.). "

" Some properties allow negative length values. "

[Extraits de la spécification sur unités relatives.

Relative length units specify a length relative to another length property.

When 'em' occurs in the value of the 'font-size' property itself, it refers to the font size of the parent element.

"h1 { font-size: 1.2em }" means that the font-size of "h1" elements will be 20% greater than the font size inherited by "h1" elements.]

[Extraits de la spécification sur unités absolues.

Absolute length units are fixed in relation to each other. They are mainly useful when the output environment is known. The absolute units consist of the physical units (in, cm, mm, pt, pc) and the px unit :

  • in: inches — 1in is equal to 2.54cm.
  • cm: centimeters
  • mm: millimeters
  • pt: points — the points used by CSS are equal to 1/72nd of 1in.
  • pc: picas — 1pc is equal to 12pt.
  • px: pixel units — 1px is equal to 0.75pt.]

[Extraits de la spécification sur rapport entre pixel vs reference pixel.

For lower-resolution devices, and devices with unusual viewing distances, it is recommended that the pixel unit refer to the whole number of device pixels that best approximates the reference pixel.

The reference pixel is the visual angle of one pixel on a device with a pixel density of 96dpi and a distance from the reader of an arm's length. For a nominal arm's length of 28 inches, the visual angle is therefore about 0.0213 degrees.

For reading at arm's length, 1px thus corresponds to about 0.26 mm (1/96 inch). [...] a reading distance of 71 cm (28 inches) results in a reference pixel of 0.26 mm, while a reading distance of 3.5 m (12 feet) results in a reference pixel of 1.3 mm.]

[Commentaire. Le W3C définit le px comme une unité de longueur absolue tout en indiquant que la longueur du pixel de référence variait en fonction de la taille de l'écran. Il faut donc plutôt considérer le pixel comme une unité de longueur relative. Pour en savoir plus : A px is not equal to a physical pixel in all cases.]

W3C, CSS 2.1, Selectors. [Les différents types de sélecteur et la contextualisation des règles.]

[Extrait de la spécification.

The following rule combines descendant selectors and child selectors : DIV OL>LI P

It matches a P element that is a descendant of an LI ; the LI element must be the child of an OL element ; the OL element must be a descendant of a DIV. Notice that the optional white space around the ">" combinator has been left out.]

W3C, CSS 2.1, Fonts. [Gestion des polices.]
W3C, CSS 2.1, Text. [Présentation du texte.]
W3C, CSS 2.1, Box Model. [Gestion des marges intérieures/exterieures et des bordures des blocs.]
maratz.com, CSS, Base Font Size -- body { font-size: 62.5%; }