I'm using up-to-date Firefox on a Mac running OS X Mavericks v10.9 This problem has been getting more and more annoying lately. When loading sites that are loading ads, Firefox locks up totally with the mouse showing the spinning beachball. I can't scroll or click on anything until the ads are finished loading. This happens across multiple sites: WUnderground.com, Yahoo.com, and even eBay.com (who just started using Google targeted ads). Has anyone seen anything like this?? Is there any way to get around it???