Nothing you can do. If you're at a site that uses Java (puzzles or anything that uses Java script) and your machine can't decipher it, you get that message. Don't bother sending the _ERR report to Sun(java) as they will tell you to send it (_err) to the operator of the site and have them correct it. Just simply delete it, as it's not a threat to your compuer.

Thanks.  What do you mean by fix it?

What causes these errors to occur?