Getting mysite?cat=1page/72/ 404 error in webmaster tool

I am continuously getting hxxp://mysite?cat=1page/72/ 404 error in google webmaster tool.
Any body know whats that????
I got 88 errors in last two days. All errors are like the one I posted above but numbers (i.e. 72 in example) keep varying.
Searched all over the google but nothing found yet.
Please guide me if anybody had this experience before.
Thank you

Anybody??

does that URL exist? and just have alook to your sitemap if there are those urls, if yes delete them and repost the sitemap

These URL's don't exist. I have checked my sitemap several times but I couldn't find them. Do you have any idea about this ??