var NS4 = navigator.appName.indexOf( "Netscape" ) != -1; //document.layers
var IE = document.all;
var IE4 = navigator.appVersion.indexOf( "MSIE 4." ) != -1;
var isMac = navigator.appVersion.indexOf( "Mac" ) != -1;
var HP = navigator.userAgent.indexOf( "HP" ) != -1;
var Sun = navigator.userAgent.indexOf( "Sun" ) != -1;
var IE5 = navigator.appVersion.indexOf( "MSIE 5." ) != -1;
var IE50 = navigator.appVersion.indexOf( "MSIE 5.0" ) != -1;
var	NS6 = navigator.userAgent.indexOf( "Netscape6" ) != -1;
var	NS7 = navigator.userAgent.indexOf( "Netscape/7" ) != -1;
var useLayers = ( NS4 && ( HP || Sun ) && !NS7 );