Six months ago I wrote about botched Windows patch KB 2670838, which caused Firefox (and apparently Chrome) to display fonts on-screen with odd rendering problems. (Here's an example, linked from the Firefox forums.)
Microsoft didn't solve the problem, but it did publish a list of video drivers thought to conflict with the patch. The company also modified the installer to avoid planting the font-busting patch on machines running the identified bad video drivers. That list, toward the bottom of article KB 2670838, has gone through eight major revisions.
I'm now seeing complaints all over the Web that installing Internet Explorer 11 on Windows 7 can trigger the same problem -- and the fuzzy fonts appear even on machines that aren't running any of the identified problematic video drivers. I'm also seeing reports that the fuzzy fonts crop up on Firefox, Chrome, and -- remarkably -- Internet Explorer itself. Some people report that the fuzziness goes away if the pages are refreshed enough times. Others see fuzzy characters only on some pages, but very similar pages don't have the problem.
If you have a case of the font fuzzies and are using IE10, the only known solution involves uninstalling KB 2670838. But if you've installed IE11, you may or may not have KB 2670838 -- and if you do have it, uninstalling doesn't fix the problem.
Microsoft has officially released IE11 for Windows 7. The IEBlog announcement goes on to say:
We will begin automatically updating Windows 7 customers to IE11 in the weeks ahead, starting today with customers running the IE11 Developer and Release Previews
Thus, at some unknown point "in the weeks ahead," your Windows 7 machines will get IE11 through Automatic Update, assuming you have Automatic Update turned on. Fuzzy fonts could be in your future. (Indeed, for Windows 8 and 8.1 users, fuzzy fonts may well be part of your fast and fluid enhanced user experience; no word on Windows RT.)
Readers have written to tell me that Microsoft's suggested solutions -- in KB 2638466 -- don't work. The solutions are also more than a bit condescending and/or misleading: "Check your viewing angle." "Upgrade your monitor." "Get good cables." "It's all in your head, take two aspirin."
If you're unlucky enough to have the wrong kind of video card and/or driver, and you're experiencing this problem after IIE11 was installed, several suggested corrections may or may not work.