How can I show a message to IE6/IE7 browsers to upgrade to IE8 and have IE8 not show the IE7 warning?

Question

I want to only allow users with IE8 (not IE6, IE7) or another browser to access my site when logged in.

I followed: http://code.google.com/p/ie6-upgrade-warning/ But

Answer 1

Probably the best way would be to detect the user's browser User-Agent string and redirect them to a page asking them to upgrade (or download a different browser such as firefox or chrome) if they are using an old version of IE. You can see examples of the user agents of IE 7 and 8 on this IE developer blog entry. Older versions of IE follow a similar pattern.

One thing you should not do, however, is assume that any user agent string not following a certain pattern is invalid. Just check for MSIE ([0-9]) and see if it's in range; if it's missing entirely, assume the browser is supported. If it's MSIE 7, then further check for the Trident marker indicating compatiblity mode (and, I suppose, ask the user to turn it off). This will allow for other, future upstart browsers to have a fighting chance at rendering your page without turning them away at the door :)