If you go to cpanel you can edit your 404 file in 'custom error pages'
I use the following :
Code:
<html>
<head>
<meta http-equiv="refresh" content="2;
url=http://www.purplegriffon.com/">
<title>Sorry Page not found -- Redirect to homepage</title>
<body>
Sorry the page you requested no longer exists you are being redirected to our home page.
</body>
<!--
So if you go to
www.purplegriffon.com/pagenothere.html you get redirected.
When I get chance I'll do something a bit fancier.