Why are there advertisements on all my browsers?

[wolf]

Whenever I open a browser like Internet Explorer, Mozilla Firefox, or even Google Chrome, there are advertisements everywhere! And the thing is is that they pop up on websites that never had advertisements! Whenever I go on Tumblr and other websites, now there's advertisements never there before and it's bothering me! I'm not sure how they got there, but now I have to use Opera because everything has advertisements. When I used adblock, they just added more ads! I don't know what to do and it's really bothering me. I want to use these browsers, but I need to know how to get rid of the ads first. Can someone please help?