I tried all of the troubleshooting tips up to and including uninstalling Firefox and reinstalling. I have no Firefox add ons, themes, or plug ins. Kaspersky Internet Security installed. A number of common, reliable sites do not render properly. Describing two in detail although there are others: In ebay, home page renders, and ebay search results appear for about 2 seconds, then disappear. On Sephora, the top menu brand selector does not work. Mouseover of brand should give a flyout menu, but with this problem you have to click the "Brands" menu item to get it to appear (www.sephora.com/brand/list.jsp). Then mousing over a letter should scroll the list of brands to those starting with that letter ... (mouseover of the letter 'K' shows the command www.sephora.com/#Meganav-brand-k ) but even with a click, the list does not scroll or move. In Edge and IE, and in Firefox on my Win 7 machine, the brand popout appears when you mouseover the menu item, and the brand list scrolls as you mouseover the letters. Neither happens in on the Windows 10 / year old Lenovo laptop. Cart loads but checkout does not work. I'm about ready to move to Chrome (Edge is just too poor a use of screen real estate). This started happening about 2 months ago - possibly with a Win 10 automated push? or with a new version of Firefox?