Without looking at your web page, if the validator is reporting hundreds of errors, you should work on fixing them. It is probably one of those validation errors that is causing your problem.
As @Gandalf says, you really need to start by fixing the errors; you can’t expect things to work correctly if they are not written correctly. There are 312 errors on that one page, 17 of them in line 471, where the problem image is. You also have a high number of CSS errors.
If you have difficulty understanding a particular message, then post it here and ask.
The good news is that fixing errors often has a “knock-on” effect; you fix one and several more are resolved as a result. So re-validate the page from time to time as you work through the errors; you might find it’s not as bad as it looks at first.
In the HTML, the 317 errors begin on line 327 with an obsolete tag, <hgroup>. You can probably replace it with a generic <div>, if it’s needed at all.
Jumping down to line 380, there seems to be a closing </p> tag without an opening <p> tag. That’s actually deceptive because all of those hyphens in a row negate what is probably supposed to be “close comment” marks and thus the </p> tag is being commented out… and so it goes. One MUST only use TWO hyphens in the open and close comment marks. Strings of hyphens are a nono.
Line 384, The validator reports that there is no space between attributes… Silly validator… it fails to mention that there are no semicolons between attributes, either. Oh, well… sometimes it expects one to know everything.
If you can clean up those three recurring types of errors throughout your page, you will probably clear most of the 317 errors reported by the HTML validator.
Why don’t you give that a try and let us know how that works for you.