var IE = navigator.appName=='Microsoft Internet Explorer'?1:0;
var NS = navigator.appName=='Netscape'?1:0;
var OP = navigator.appName=='Opera'?1:0;
var VS = parseInt(navigator.appVersion);
if( !(IE|NS|OP) )alert('This browser:\n'+navigator.appName+' '+navigator.appVersion+'\nmay not be compitable');

var IE4a = 0;
var NS4a = 0;
var NS6a = 0;
if(IE&&(VS>=4)) { IE4a = 1; }
else if(NS&&(VS>=5)) { NS6a = 1; }
else if(NS&&(VS>=4)) { NS4a = 1; }