tag in url

I’ve noticed that my site generates URLs that contain a tag in them, for instance:

http://www.domain.com/tagA
http://www.domain.com/tagB etc’, etc’ for all my tags

I know this since I use a plugin that shows 404 errors and all of those types
of URLs end up as 404 errors(at least for my site)

I do not want these URLs to be generated, so is there a plugin that prevents the automatic creation of domain.com/tag