h = 340
w = 290
var w_avail = screen.availWidth;
var h_avail = screen.availHeight;
var top = Math.round ((h_avail - h) * .5);
var left = Math.round ((w_avail - w) * .5);
var newWin = null; 
newWin = window.open('http://www.profitrally.com/popup/popup.phtml?sponsor=thenutrishop',newWin,'width=' + w +',height=' +h + ',left=' + left + ',top=' + top + ',resizable=1, scrollbars=1');
newWin.focus();