Image sometimes doesn’t load for onmouseover

First of all, I know nothing about JavaScript, I got this code from [url]http://www.dynamicdrive.com[/url] and basically just copy-pasted.

So I’m using a code for a mouseover image change for a menu at

[url]http://www.happinesshypothesis.com[/url]

It’s working fine, except that at really random intervals, the regular, not mousedover image for one of the menu links doesn’t load and has the broken image icon. Most of the time it works just fine, but every so often it won’t load. Like I said, I know nothing of Javascript and when this code is run through an HTML validator it doesn’t accept hsrc part. Any explanations or advice as to solve this problem or for a better mouseover code would be appreciated. Thanks =)

-Natalie

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