Missing logos and pictures?

My son has tampered with my PC and told me that he ticked or unticked something somewhere when he was trying to get something to come up on screen. Apparantly it was something that the Channel 5 TV said he needed to do in order to watch a repeat program, something to do with ad-blocking software but I don't know what he clicked on and it didn't work anyway. Now as I was about to print an e-ticket I notice that I'm getting the little squares with a red cross where obviously a picture or logo should be. How do I get it back to normal? Where do I find what to tick and/or de-tick?