function speed_test()
{
    var a=1,b=3,pi=0,test=120000;
    
    //cause IE is slow...   
    var ie = ( typeof window.ActiveXObject != 'undefined' );
    if(!ie)
        test = test * 35;
    
    //chrome IS slower than ff, I told you chris :P
    var chrome = navigator.userAgent.toLowerCase().indexOf('chrome') > -1;
    if(chrome)
        test = test/4.5;


    t1=new Date();
    for(var i=0;i<test;i++)
    {
        pi=pi+(4/a)-(4/b);
        a+=4;
        b+=4;
    }
    t2=new Date();
    
    //debug
    //alert((t2.getTime()-t1.getTime())/1000);
    
    if(((t2.getTime()-t1.getTime())/1000) < 0.1)
    {
        var e = document.getElementById('background');
        e.style.display = 'block';
    }
}