Markup validation-general entity "s"

[karabaja]

I tried w3c markup validator on my board and I noticed these errors:

cannot generate system identifier for general entity "s".

<a href="forumdisplay.php?f=1&s=xxxxxx&amp;"><b><font 

general entity "s" not defined and no default entity.

<a href="forumdisplay.php?f=1&s=xxxxx&amp;"><b><font 

reference not terminated by REFC delimiter.

<a href="forumdisplay.php?f=1&s=xxxxxx&amp;"><b><font 

reference to external entity in attribute value.

<a href="forumdisplay.php?f=1&s=xxxxxxx&amp;"><b><font

Few months ago my site passed w3c validation, I have other errors besides this one related to session id, but those I'll probably manage to fix. But I am curious what is causing this one. Since I don't see it on other boards I administer. Not sure what is different, I guess it could be some modification, but I'd appreciate if anyone has some suggestions.

P.S. had to replace sessionid with xxxx as it disappears after I post it in code tag.

[Floris]

The &s= instead of &s= gives away (especially since it is behind the ?f= part) that this might be from a modification?

The ? in the url will include the session for that user, and usually & is set as & in vB (should be in my eyes), and as far as I know it starts with it, not puts it halfway through.

[karabaja]

Thanks Floris, the problem was I didn't have "&" alone anywhere in templates. It is set correctly as "&" everywhere.
So I disabled modifications one by one, and the one that turned out to be the cause was Zoints seo. I've removed it now, everything is fine. I was really using it anyway, just one function, that is to display "all" link when listing pages of some forum. And for adsense in archive. But I can live without all link, and there is other ways to include adsense in the archive.
Anyway, I am glad it is sorted.