Well, personally, sometimes dealing with validator make me a bit confuse. But, as long as we didn't miss important tags, I think we will not get a huge error. You can see it in you page source.
Try to fix the error step by step. At least for the first three error:
1. You missed the <tr> tag after the <table> tag.
Find this in your forumdisplay or something like that template:
You should have <tr> tag before the tag above.
2 and 3. Your image tag in the part above:
You should add alt attribute in the tag. And self close the tag: