This document explains how to clear the cache and cookies in Internet Explorer 9 on Windows Phone devices.
Tap the Internet Explorer live tile on the home screen.
Tap on the ellipses (...) at the bottom right.
Scroll down and tap settings.
Scroll down and tap delete history.
Tap delete to confirm.
Wait a few seconds for the cache and cookies to clear. Then, you can tap the back button to return to Internet Explorer.