Conformance requirements on browsers

I have used to say that HTML5 declares many HTML features as not 
conforming, still requiring user agents to keep supporting them. For 
example, a document that uses the <font> tag is not conforming, but 
browsers must support it. This seems evident from clause 2.2.1 and from 
the detailed description of the effect of the font element (in 10.3.4).

But now I started wondering what is e.g. the status of the (widely 
supported) @background attribute in <td>. It is just mentioned in 11.2, 
in a long list of obsolete attributes, with the note "Use CSS instead."

So how does the requirement "must process elements and attributes [...] 
as described in this specification" or "must process documents [...] as 
described in this specification" (in 2.2.1) apply to, say, obsolete 
attributes that are just mentioned with no real *description*?

If browsers are required to support, say, the @background attribute in 
<td>, how can you decide whether a browser meets this conformance 
requirement, when it has no description?

On the other hand, if browsers are not required to support it, we have 
actually three kinds of obsolete features:
1) obsolete but conforming
2) obsolete and non-conforming, but browser support is required
3) obsolete and non-conforming, and browser support is not required

I think this should be clarified in 1.2.2.

-- 
Yucca, http://www.cs.tut.fi/~jkorpela/

Received on Wednesday, 11 September 2013 11:17:41 UTC