I was trying to implement the Adgator code for a Blogger blog and my efforts was frustrated by the infernal XML error *message: The reference to entity “whatever” must end with the ‘;’ delimiter.
The solution was (eventually) fairly simple – isn’t it always.
Look for & in the code.
Change every instance of & to & a m p ;
This should work in WordPress and most other blog applications as well.
In the case of Blogger / Blogspot blogs this was used successfully in the theme file HTML. This was also reported to work in a Blogger post.
For Adgator users I suggest using the WordPress Code for your blogs. You will find a link to this code on the bottom of your “Get Ad Codes”-page.
*whatever can of course be anything in your case.