function Is() {
var agent = navigator.userAgent.toLowerCase();
this.major = parseInt(navigator.appVersion);
this.minor = parseFloat(navigator.appVersion);
this.ns = ((agent.indexOf('mozilla')!=-1) &&
((agent.indexOf('spoofer')==-1) && (agent.indexOf('compatible')== -1))); 
this.ns4 = (this.ns && (this.major >= 4));
this.ie = (agent.indexOf("msie") != -1);
this.ie4 = (this.ie && (this.major >= 4));
}
var is = new Is();
var w=810;   //set Width for window 
var h=708;   //set Height for window
if(is.ns4){             
window.outerWidth  = w; 
window.outerHeight = h; 
var Xcor = (screen.width-window.outerWidth)/2; 
var Ycor = (screen.height-window.outerHeight)/2
window.moveTo(Xcor, Ycor);
}
else if(is.ie4){         //if Internet Explorer 4
//i'm designing this page for no toolbars if you will use toolbars put this line in h+=10;
//IE toolbars are a bit smaller so some area will be covered that you see in NN if you add 10 pix that compensates
var Ycor=(screen.height-h)/2;
var Xcor=(screen.width-w)/2;
window.moveTo(Xcor, Ycor);window.resizeTo(w,h);
}