This is an example of moire patterns that need to be removed from scans before posting.
Many scanning software packages have an option to remove moire patterns if your's has it you should enable it. This usually the best way to deal with the problem. Your scanning software may also refer to Moire Patterns as Halftone Dots same thing.
In addition the scanning tutorial on the site has a section on how to deal with moire patterns using photoshop you can get a copy of it here.
Link To Download The R1DB Scanning Tutorial