Test your sites on IE 11 (just out)
 

Test your sites on IE 11, just out for Win 7, and around on win 8.1 since a while.

Lots of jscripts may not work.
If your site is victim of IE11 update: to solve, add this meta tag in the header:

<meta http-equiv="X-UA-Compatible" content="IE=10">

It will let IE11 work like IE10 (and no effect on older browsers).

If you want to fix on IE11 by hand:

Most of the issues arise from attachEvent (that was an IE only version of addEventListener) being replaced with addEventListener. This would be great, that IE became finally compatible with other browsers. But most of the old scripts check if IE, if IE use attachEvent , else addEventListener. They detect IE and use attachEvent which is no more there and crashes/stop execution.

More code details here:

http://msdn.microsoft.com/en-us/libr...spx#legacyAPIs

PS: Really no one "Twitter IPO" threads in GFY, or I missed it? GFY is no more a reliable source of offtopic info as it once was...