getInternetExplorerVersion()

gistfile1.js

function getInternetExplorerVersion()
// Returns the version of Internet Explorer or a -1
// (indicating the use of another browser).
{
        var rv = -1; // Return value assumes failure.
        if (navigator.appName == 'Microsoft Internet Explorer')
        {
                var ua = navigator.userAgent;
                var re  = new RegExp("MSIE ([0-9]{1,}[\.0-9]{0,})");
        if (re.exec(ua) != null)
                rv = parseFloat( RegExp.$1 );
        }
        return rv;
}