need fix for bad html

With recent changes in IE, we've discovered Drupal is producing bad html (including some unclosed tags). Have you all experienced this, and have you found a fix?

Here's my example:

The Announcements Header (News & Events | Archive) is crossing under the photo only in IE. It displays properly in Safari and Firefox. Believed to be an unclosed tag issue.

Also, only in IE the dropdown menus on the navigation bar are not displaying properly (sub navigation is crossing under the drop down—see Working Groups).