We find our posts on our site contain invalid HTML. This is not specific to our site, it can be seen on this site as well. This example demonstrates the error:

http://telligent.com/support/f/533/t/1074841.aspx

You can see the errors here - the particular error is at line 681.

http://validator.w3.org/check?uri=http%3A%2F%2Ftelligent.com%2Fsupport%2Ff%2F533%2Ft%2F1074841.aspx&charset=%28detect+automatically%29&doctype=Inline&group=1&user-agent=W3C_Validator%2F1.3+http%3A%2F%2Fvalidator.w3.org%2Fservices