Welcome to the forums, please review our
Posting Policies especially in regards to #8 (scroll down the page) posting computer code
you need to use the prefix document to tell the browser you are talking about this specific page, you also are calling out multiple images by the same name attribute, thus confusing the browser even more.
Code:
<img src="MainMen.jpg" name="MainMens" width="500" height="400">
<a href="/path/to/link" onmouseover="document.img1.src='/path/to/image.ext';document.MainMens.src='/path/to/image.ext';"> LINK</a>
<img src="/path/to/image" name="img1" width="" height="" alt="__alt_desc__">
<a href="/path/to/link" onmouseover="document.img2.src='/path/to/image.ext';document.MainMens.src='/path/to/image.ext';"> LINK</a>
<img src="/path/to/image" name="img2" width="" height="" alt="__alt_desc__">
where img# is the unique identifier of that specific
Bookmarks