FWIW - I've just done several tests with syntax offered in the prev
It boils down to this, out of the browsers tested below, only Safari
uses the Labels text if it provided. Otherwise all other browsers use
the text between the Option tags.
Win2K IE5 -- doesn't support the optgroup
Win2K IE5.5 -- didn't test
Win2K IE6.0 -- uses option text
Win2K Firefox 1.0.4 -- uses option text
WinXP IE6.0 -- uses option text
WinXP Firefox 1.0.4 -- uses option text
OS X (10.3) Opera 6.0 -- doesn't support the optgroup
OS X (10.3) Opera 7.5 -- uses option text
OS X (10.3) Firefox 1.0.4 -- uses option text
OS X (10.3) Safari 1.0.4 -- uses labels text
Didn't test any Linux browsers.
I found with FireFox that if you CSS style the <select> tag to change
the font, you also have to style the optgroup tags, and if you style
the optgroup tag, you also have to style each option tag inside that
optgroup. So for best uniformity across all browsers, once you use
optgroup if you apply a CSS class to the select tag, you have to apply
it to every optgroup and option tag as well.
At first it feels like Safari is wrong, but it seems that it has the
better behavior because you could use the Labels for the optgroup
strings, and the standard strings for when optgroup is not supported.
So the browsers that are supporting optgroup should be rendering the
Labels text IMO, but I didn't reread the RFC to see what it specs.