Can't stop Pop up ads on yahoo home page

Hi,

I have 3GS with latest 4.3.3 os. Last couple of days, every time I open yahoo home page (uk.m.yahoo.com) I get pop up ad at bottom of the page. Clicking on the close button only removes it to a tap that appears at edge of screen. If I open the ad to full page and close the ad it doesn't disappear but goes back to sitting at the bottom of the page again. The ad is for the 'green lantern' or 'lynx body spray'. I've been into safari settings and the block pop ups is on. I've cleared history, cookies and cache, Rebooted iPhone but it keeps appearing.

This pop up is really annoying and blocks the view of the bottom of the screen! Never had this problem til couple of days ago. I'm on a data plan so it's not because I'm pay as you go.

Any help would be appreciated as it's driving me nuts!