Favorite links being rerouted to other sites? 0_o

[Cannonfury]

I don't know why or how but on my list of favorite sites, when I click a link it sends me to something else. I have Firefox. For example...I click the link that goes to yahoo.com but it sends me to a blank white page with a picture of a pof or disney pirates banner....or I click the one for my schools website and it tries to go to another site but my browser doesn't let it load all the way, it shows a message saying that my browser has blocked this site because it could be dangerous...and no I dont have a virus protection cause mine expired months ago... thought about using Avast(i think that's what its called)