phranque - 1:25 pm on Jul 18, 2013 (gmt 0)
welcome to WebmasterWorld, kartoshka!
i assume GWT was reporting these as 404 or 410 (Not Found) "errors"?
if they don't exist and you're not linking to those urls internally then it's not a problem.
it could be that google discovered some of these urls elsewhere.
if it is a problem on your end (such as the erroneous inclusion in your sitemap) they are reporting these for your convenience so you may fix the problem.
since it occurred right after a redesign, i would suggest using a site crawler to see if you are linking to any of these urls internally.
if you return a 410 Gone status code instead of a 404 Not Found they should disappear soon(er).