Without the full HTML source code, I'll point to that this anchor is nested or after to some element that doesn't have a closing tag.
Post full HTML source code if this isn't the problem.
You can find this problem easly by validating your document with:
It's the W3C official HTML/XHTML validator, so if some element isn't closed, it'll point which one you need to correct!
EDIT:
After watching your HTML source code posted in answer's comments... where's the document type (DOCTYPE) declaration? You forgot to add it!
Add this at the beginning of your HTML document:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
When you don't provide a document type, browsers render web pages in "quircks" mode, which is a compatibility mode that may not render your page as you expected. Learn more about that here:
Let me know if this solves your problem!