Tools>Internet Options - Security tab, click "Reset all zones to default"
If your web pages do not work in a version of IE but does work in the 'other' browsers then it is because of IE's security zone settings.
Always target IE's default security zone settings. What zones are your index and frameset pages loading in?
Also validate your frameset (index) and iframe page at validator.w3.org (F12>Validate>Markup). IE is now more standards compliant and is less
tolerant of malformed markup (viz... does not fill in the blanks).
Usually during testing I turn off "Automatically recover from rendering errors with Compatibility View" on the Advanced tab of Internet Options to
make sure IE8 DOES NOT try to correct my mistakes with compatibility view. Code to the standards of your chosen DTD and IE works fine, feed it junk and it can choke or trip to IE7 emulation mode.
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