function isThisBrowserIE6()
{
   var is_ie = $.browser.msie;
   var has_ie6_features = ((window.XMLHttpRequest == undefined) && (ActiveXObject != undefined));

   var is_ie6 = has_ie6_features && is_ie;

   return is_ie6;
}

$(document).ready(function()
{
    if(isThisBrowserIE6())
    {
        $("#unsupported_browser").removeClass("hidden");
    }
});