everytime i open a new tab, it isn't blank. Yahoo! search page opens in the new tab. How do i change this back to a blank page? I am not a fan of Yahoo..

I downloaded a program recently and one of it's 'addition downloads' was making Yahoo! my homepage and making new tabs open Yahoo! instead of just a blank page . Tried to cancel before it was done it was too late. I have changed my homepage back to my default homepage but I cannot find the Tab settings to change it back to a blank page when I open a new tab. I do not want Yahoo! opening every time I open a new tab. please help.