The interesting point about the entire <link rel="icon" issue is that it is a crutch to get past a shortcoming in IE. I admin a handful of boards and in every instance, IE is the only browser that could not properly display favicon. And once the page is saved in the IE Favorites folder, <link rel="icon" becomes totally unnecessary, as IE will then display it.

I ran the X Marks CMPS page through your W3C validator and quite interestingly enough, not a single lick of the vBulletin code was reported. Some older code that was brought in from modules created in an earlier version of the CMPS was all that was reported.

And the entire issue of W3C validation really fails to answer the earlier question as to whether or not your browser is displaying the favicon.