Thanks for the answers to my previous ques..but I used to not see the squares in the corners it has just start

I used CCleaner awhile back an I think maybe I deleted something that I wasn't supposed to? I used to have no problems with seeing any pics..I have clicked on the right and highlited show pic and it works...but this is only happening in my email on yahoo...what the heck have I done? and I hope there is a way that I don't always have to right click and show picture...I want it back the way it was before...Can anyone tell me how and what I need to do? System Restore ? but I don't want to do restore if it isn't necessary??????