When submitting a form on my site, the user is redirected to the third party email campaigns site. When redirected back to my site the favicon of the third remains on my page. How can I get rid of it?
This could happen if you don't have a favicon on the site itself (If you don't want/have a favicon that you'd want to use, you can use an empty image for a favicon).
For best compatibility, I'd suggest having both a /favicon.ico, and a link to it in your HTML document, as seen e.g. here: http://en.wikipedia.org/wiki/Favicon#Accessibility