Category Archives: Style

StyleSheets, design and related issues.

The <b> and <i> Elements

Over on public-html (and cross posted to www-html), there is some intense bikeshedding going on pertaining to the use of the b and i elements and why they should or should not be retained in HTML 5. Some have argued that b and i are strictly presentational elements, and that they should not be retained in HTML5.

Others have argued that the b and i elements are virtually synonymous with strong and em in reality, so trying to define otherwise is pointless. The reason that i and b could be considered synonymous with em and strong, respectively, has to do with them being used largely interchangeably with each other in reality, and very little to do with their actual definitions.

However, it’s reasonable to hypothesise that there would be significantly more non-emphasis-usage of i than there would be usage for emphasis, and so defining that all uses of i represent emphasis would be a mistake (similarly for b and strong).

Therefore, the pragmatic approach is to specify that i and b convey unspecified semantics, which are to be determined by the reader in the context of their use. In other words, although they don’t convey specific semantics by themselves, they indicate that that the content is somehow distinct from its surroundings and leaves the interpretation of the semantics up to the reader.

That is effectively the approach taken by the HTML5 spec. These are the current definitions for the b and i elements.

The b element:

The b element represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as key words in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is boldened.

The b element should be used as a last resort when no other element is more appropriate. In particular, headers should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked or highlighted should use the m element.

The i element:

The i element represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, a ship name, or some other prose whose typical typographic presentation is italicized.

Terms in languages different from the main text should be annotated with lang attributes (xml:lang in XML).

The i element should be used as a last resort when no other element is more appropriate. In particular, citations should use the cite element, defining instances of terms should use the dfn element, stress emphasis should use the em element, importance should be denoted with the strong element, quotes should be marked up with the q element, and small print should use the small element.

Context is effectively how users distinguish between italics used for emphasis and the variety of other uses, so providing a couple of catch-all elements for the remaining cases that don’t have specific elements, isn’t all that bad.

The separation of presentation and semantics isn’t a goal in and of itself that needs to be strictly adhered to. Rather, it’s just a means to an end and if that end can be reached without a strict separation, then so be it.

The Cascade: Part 2 (Finally!)

Exactly one year ago from this day, I published part 1 in a series of articles about CSS cascading and inheritance. However, due to various factors (mostly laziness), the sequel never got published… Until now! Today, I’m going to take a break from the XBL series of articles (which will resume in a day or so) and finally publish the long awaited conclusion to this series. If you haven’t read part 1 (or even if did a long time ago), I suggest you do so now before continuing.

Following on from the first article in which we looked at how to find all the style declarations that applied to each element, we’re going to show how these are sorted by order of precedence, to determine which ones are applied to the element.

Sorting

Steps 2, 3 and 4 of the algorithm deal with sorting the declarations into the order of precedence. From the exercise in the part 1, we were left with 4 rule sets which applied to the p element in the sample document. For the purpose of this exercise, I’m just going to add a few more declarations and annotate them with their origin.

p { margin: 1em 0; } /* User Agent */
* { background: blue none !important; color: white !important; } /* User */
P { text-indent: 1em; text-align: left; } /* User */
p { text-align: justify; } /* User */
#content p { margin: .8em 0; line-height: 1.2; text-indent: 0 !important; } /* Author */
p { line-height: 1.4; } /* Author */

Step 2

Step 2 of the cascade says to sort the rules according to importance and origin. The following is the order of precedence specified in CSS 2.1.

  1. user agent declarations
  2. user normal declarations
  3. author normal declarations
  4. author important declarations
  5. user important declarations

If we discard the selectors for now (they’ll be need again in step 3 below), we’re left with a list of declarations. A declaration is a property and its associated value. We can then proceed to sort them into the order specified.

  1. User Agent Declarations
    1. margin: 1em 0;
  2. User Normal Declarations
    1. text-indent: 1em;
    2. text-align: left;
    3. text-align: justify;
  3. Author Normal Declarations
    1. margin: .8em 0;
    2. line-height: 1.2;
    3. line-height: 1.4;
  4. Author Important Declarations
    1. text-indent: 0 !important;
  5. User Important Declarations
    1. background: blue none !important;
    2. color: white !important;

Step 3

Step 3 of the cascade then says to sort the rules with the same importance and origin by the specificity of the selector. The details of calculating the specificity is out of scope for this article, but it has been covered by others. See Andy Clarke’s Specificity Wars and Molly Holzschlag’s CSS2 and CSS2.1 Specificity Clarified.

This step is important for cases where two declarations for the same property have the same importance and origin. In this example, this occurs for both user normal declarations (two text-align declarations) and author normal declarations (two line-height declarations).

For the user normal declarations, these are the rule sets involved:

p { text-indent: 1em; text-align: left; } /* User */
p { text-align: justify; } /* User */

As you can see, both have the same selector (p), which has a specificy of 0,0,1. So, sorting by specificity in this case makes no difference. However, for the author normal declarations, these are the rule sets involved:

p { line-height: 1.4; } /* Author */
#content p { margin: .8em 0; line-height: 1.2; text-indent: 0 !important; } /* Author */

These 2 rule sets each use different selectors which have different specificity. The selector #content p has a specificity of 101. The selector p has a specificity of 0,0,1. Since 1,0,1 is a higher specificity than 0,0,1, the former takes precedence. So the order of author normal declarations is changed to the following:

  1. margin: .8em 0;
  2. line-height: 1.4;
  3. line-height: 1.2;

Step 4

The forth and final step of the sorting process involves sorting declarations which have the same importance, origin and specificity by the order they are specified in the CSS. This is where the order of the user normal declarations from step 3 is resolved. In this example, given that I listed the declarations in the order in which they appeared, no change needs to be made to the above list.

In cases where there is more than one declaration for a property, the latter declaration overwrites the former, which is effectively discarded. This leaves the following list of declarations to be applied to element.

  1. text-align: justify;
  2. margin: .8em 0;
  3. line-height: 1.4;
  4. text-indent: 0;
  5. background: blue none;
  6. color: white;

This concludes the series about the cascade, but the related issue of inheritence still needs to be addressed and I intend to do so at some point in the future. However, I don’t expect that it will take another year before I do… But who knows? :-)