Are Property Values In CSS Case-sensitive?


Answer :

(updating @ÁlvaroG.Vicario answer and comments, and complementing this answer... This is a Wiki, please edit to enhance)

Example: for CSS3 (and HTML5) there are new explicit rules, as "font-face property must be case-insensitive".[2]

Context

W3C interoperating standards, mainly XML, HTML, CSV and CSS.

CSS general rules

CSS2 (a W3C standard of 2008) fixed basic conventions about "Characters and case", and CSS3 (a W3C standard for 2015) added something more.

  1. By default "all CSS syntax is case-insensitive (...)" [1]

  2. There are exceptions, "(...) except for parts that are not under the control of CSS"[1]

    2.1. element names are case-sensitive in HTML5 (?) and XML, but case-insensitive in HTML4.

    2.2. identifiers (including element names, classes, and IDs in selectors) are case-sensitive. HTML attributes id and class, of font names, and of URIs lies outside the scope of the CSS specification.

  3. ....

  4. The

Case matrix

Exceptions and specific (explicited in a reference) rules. "YES" indicate that value is case-sensitive.

Property values:

 CSS property      | Case-sens. | Reference and notes  ------------------|------------|--------------------  %colorVals        | NO         | [3]  font-family       | NO         | [2]  %url              | YES        | ...  content           | YES        | ...  ----------------------------------------------------  %colorVals = color, background, etc.  %url = background-image, etc. that use `url()`, see [7] and notes.

Selector values:

 CSS selector      | Case-sens. | Reference and notes  ------------------|------------|--------------------  id                | YES        |...  element           | YES/NO     | ... YES for XML...  class name        | YES        | [5]  (`~ i` operator)  | NO         | [6]  ----------------------------------------------------  YES/NO = depends on the document language (see ref. and notes).

REFERENCES:

[1] W3C/CSS2/syndata, sec. 4.1.3 Characters and case.

[2] W3C/CSS3-fonts, sec. 5.1 Case sensitivity of font family names

[3] W3C/CSS3-color, sec. 4.1. Basic color keywords

[4] W3C/CSS3-values, sec. 3.1. Pre-defined Keywords

[5] W3C/Selectors, sec. 3. Case sensitivity

[6] W3C/Selectors4, sec. 6.3. Case-sensitivity

[7] RFC 3986 and URL syntax illustration at Wikipedia.

Quotations and notes

  • Typical URLs starts with domain, that is case insensitive, but after it (path, query or fragment syntatical components), is case sensitive. See [7].

  • "User agents must match these names case insensitively". [2]


The spec for CSS 2 says:

CSS syntax is case-insensitive within the ASCII range (i.e., [a-z] and [A-Z] are equivalent), except for parts that are not under the control of CSS. For example, the case-sensitivity of values of the HTML attributes "id" and "class", of font names, and of URIs lies outside the scope of this specification. Note in particular that element names are case-insensitive in HTML, but case-sensitive in XML.

... which makes quite sense: CSS itself accepts both background-image and BACKGROUND-IMAGE but it has no way to know whether your web server considers LOGO.PNG and logo.png as identical or different resources.

(I've been unable to find the equivalent document for CSS3)


Comments

Post a Comment

Popular posts from this blog

Chemistry - Bond Angles In NH3 And NCl3

Answer : Solution 1: As Tan Yong Boon stated, it is Bent’s Rule with which we can explain the lower bond angle of \ce N F 3 \ce{NF3} \ce NF 3 when compared to \ce N H 3 \ce{NH3} \ce N H 3 . The rule as stated by Henry Bent: Atomic s character concentrates in orbitals directed towards electropositive substituents. Fluorine is more electronegative that hydrogen, and the \ce N − F \ce{N−F} \ce N − F bond would have greater p character than the \ce N − H \ce{N−H} \ce N − H bond. And more s character leads to large bond angles. Thus, the bond angle is greater in \ce N H 3 \ce{NH3} \ce N H 3 than in \ce N F 3 \ce{NF3} \ce NF 3 . Now, consider \ce N C l 3 \ce{NCl3} \ce NCl 3 . Clearly, \ce C l \ce{Cl} \ce Cl atom islarger in size than the central atom, nitrogen. Hence the higher bond angle here is due to the steric crowding caused by \ce C l \ce{Cl} \ce Cl atoms.(More pronounced than the electrongativity of \ce C l \ce{Cl} \ce Cl atom). They repel eachother and hence b
Read more

Are Regular VACUUM ANALYZE Still Recommended Under 9.1?

Answer : VACUUM is only needed on updated or deleted rows in non-temporary tables. Obviously you're doing lots of INSERTs but it's not obvious from the description that you're also doing lots of UPDATEs or DELETEs. These operations can be tracked with the pg_stat_all_tables view, specifically the n_tup_upd and n_tup_del columns. Also, even more to the point, there is a n_dead_tup column that tells, per table, how much rows need to be vacuumed. (see Monitoring statistics in the doc for functions and views related to statistics gathering). A possible strategy in your case would be to suppress the scheduled VACUUM, keeping an eye on this view and checking on which tables the n_dead_tup is going up significantly. Then apply the aggressive VACUUM to these tables only. This will be a win if there are large tables whose rows never get deleted nor updated and the aggressive VACUUM is really necessary only on smaller tables. But keep running the ANALYZE for the optimiz
Read more

Can Feynman Diagrams Be Used To Represent Any Perturbation Theory?

Answer : Diagram machinery works also for perturbation theory in classical statistical mechanics and classical field theories. Generally, various kinds of diagrams constitute a pictorial way of talking about tensor products and their contractions while hiding the multi-linear algebra from the layman. In the simplest case, vertices (or blobs) represent vectors, matrices, tensors; vertices have ingoing and/or outgoing ports; ingoing ports denote (contravariant) ro indices; outgoing ports denote (covariant) co indices; directed arcs between blobs give a pair of equal indices summed over; different base spaces ⇔ \Leftrightarrow ⇔ different arc types; symmetric tensors ⇔ \Leftrightarrow ⇔ undirected diagrams; no labels are needed for internal lines. In many cases, the directed arcs are decorated (as thin, thick, broken,wavy, curly lines), each decoration indicating the presence of a so-called propagator, a function of its label to use as a weight in the sum, which may beco
Read more