It seems that most affiliate programs (e.g. Amazon, Linkshare, etc.) provide non W3C compliant XHTML code fragments. When I use the W3C validator I get hundreds of errors and warnings on any pages that use affiliate links.
Mostly the issues are non-encoded special characters, but there are other problems too.
I'm a bit worried about the impact on SEO, but it also just clutters the validator output and makes it extremely hard to use.
If you use affiliate links, how do you deal with this? Hand-correct the markup?
Does it matter?