Hello,
I found another training by Nathaniell, his training are usually right on spot. If the one listed by Boothe doesn't help, try this one. I've also been told those errors are not a huge deal, so breathe sister! It'll be alright. Fix Not Found Errors in Webmaster Tools

If I remember correctly these errors are not a big deal but it's always good to fix them anyway because they will help your rankings. This particular one might be related to your theme...

You might want to do a quick google search on how to fix that type of error. Also, this webinar might help: Insights into Webmaster Tools