On April 8, 2014, Microsoft officially ended support for Windows XP operating system, which was a long time coming - after all, those Windows 8.1 packages are not going to sell themselves. With that, the entire suite of software products associated with older OS, including IE8, lost support and future critical updates and currently presents a potential security issue.
Fear mongering aside, we advise all our agency partners and their respective clients to take Microsoft’s notice under consideration, as we also will be no longer supporting IE8 development to avoid potential security issues with end product.
http://www.microsoft.com/en-us/windows/enterprise/end-of-support.aspx