Internet Explorer 10's "Modern" (or "Metro") mode includes limited support for Adobe's Flash Player plugin – websites approved by Microsoft can access Flash, unapproved sites cannot. Fortunately, intrepid Windows 8 users have already found an easy way to extend Flash support to any website.
Microsoft originally planned to leave Flash out of the tablet-friendly version of IE10, but later changed its mind. Dean Hachamovitch, Internet Explorer VP, said at the time that Microsoft "believes that having more sites 'just work' in the Metro style browser improves the experience for consumers and businesses alike."
But the only time Flash "just works" in IE 10's Metro mode is when you visit sites Microsoft has approved. Developers can submit their sites to Microsoft for approval, but if you'd like to take matters into your own hands, user Marvin_S at the XDA Developer forums has figured out how to add whichever sites you like to Microsoft's whitelist. To edit the whitelist, just open the file C:\Users\[USER_NAME]\AppData\Local\Microsoft\Internet Explorer\IECompatData\iecompatdata.xml in a text editor of some kind. Then add whichever domains you'd like to be able to access the Flash Player.
To make sure that your custom whitelist isn't overwritten when Windows 8 updates the list, open IE 10's Tools menu and select the Compatibility View option. Then uncheck the box labeled "Download updated compatibility list from Microsoft."
Be forewarned that one of the reasons Microsoft has limited which sites can access Flash is to limit security vulnerabilities; editing the whitelist yourself and turning off updates may expose you to Flash-based attacks, especially given that during the testing phase of Windows 8 Microsoft was slow to apply Flash updates.
