Mac OS X on my computer and lately getting an error

Hi,
I have Mac OS X on my computer and lately I am getting an error as soon as my computer boots. I do not remember installing an application of late but maybe one of my friend’s did since I share my computer if need be.

There was a problem with an alert.
The “open file” alert that was assigned to the event ™ didn’t run on 28 February 2013 because Block sites 8 hours New.app couldn’t be opened.
