404 errors

I looked at Webmaster tools and found that I have 404 errors on pages, it also says that there are images with 404 errors but these pages & images are not on the site, I have looked at deleted items & draft items and there is nothing in there.

Some of the URL’s that its saying has errors is something like screen-200px/ or screengrab-2/ or features-2 but the URL on the site is features

Would appreciate if someone would help me

Many thanks