Awesome Screenshot is known to inject additional ads. I would suggest that you remove it.
See this site for additional information and also a way to remove it if you wish.
http://www.thesafemac.com/screenshot-extension-injects-ads/
I'm not sure what the extension claims to do, but OS X already has two pre-installed screenshot tools.
One, is to simply using the keyboard shortcuts
http://support.apple.com/kb/HT1343?viewlocale=en_US&locale=en_US
Your screen shots can then be opened in Preview if you want to mark them up
Second, Grab.app which is in your Applications/Utilities folder