function centerPopup(url, width, height){ var wnd; var left = (screen.width / 2)-(width/2); var top = (screen.height / 2)-(height/2); wnd = window.open(url, '', 'width='+width+', height='+height+',left='+left+',top='+top); } E então faça o link assim: <a href="java script:centerPopup(nome_da_janela.html',770,610);">link</> ONDE 770 e 610 é o tamanho do pop-up.