Possible Duplicate:
Javascript redirect for Internet Explorer browser version user agent?
Detect IE version in Javascript
What is the best practice if I do not want to allow any users to use the site unless they have ie9 or higher, or firefox/chrome/safari. ie7 and ie8 should not work and it should redirect to a notification page that tells the user to upgrade his or her browser. Is this even the best practice for this situation? If so, how would the code look in javascript.