alignment of attachment and user profile picture icons

I noticed that the logo for pdf and user profile pic attachments on the Dashboard have an extra line near them (see attachment). The sprite is correct but the pixels on the css are 2px out.

In the css if I change the value for background position from 312 to 314
(314px top) it looks correct.

minor but annoying. I think it occuring acros all background positions but is noticeable on pdf's as you get a bit of the symbol next to it.