+ <h4>Attributes common to <code>td</code> and <code>th</code>
elements</h4>
+ <p>The <code>td</code> and <code>th</code> elements may have a <dfn
+ title="attr-tdth-colspan"><code>colspan</code></dfn> content
+ attribute specified, whose value must be a <span>valid non-negative
+ integer</span> greater than zero.
Isn't that the description of a valid positive integer? If that term
is not used or defined yet, why not?
+ <p>The <code>td</code> and <code>th</code> elements may also have a
+ <dfn title="attr-tdth-rowspan"><code>rowspan</code></dfn> content
+ attribute specified, whose value must be a <span>valid non-negative
+ integer</span>.
Why can |rowspan|, unlike |colspan|, be 0, but is then also
normalised to 1?
