此方法可通用，项目开发中经常要用到：

//w:宽，h:高，url：地址，tag：标记
function showWin(w, h, url, tag) {
 var t = (screen.height - h) / 2; //离顶部距离
 var l = (screen.width - w) / 2; //离左边距离
 window.open(url, tag, "width=" + w + ",height=" + h + ",top=" + t + ",left=" + l + ",location=0");
}
//路径地址，window对象，宽，高
function open_Dialog(url, win,Width, Height) {
    var return_Value;
    var iTop2 = (window.screen.availHeight - 20 - Height) / 2;
    var iLeft2 = (window.screen.availWidth - 10 - Width) / 2;
    var height2 = Height - 50;
    if (document.all && window.print) {
        return_Value = window.showModalDialog(url, win, "dialogLeft:" + iLeft2 + "px;dialogTop:" + iTop2 + "px;dialogWidth:" +
 Width + "px;dialogHeight:" + Height + "px;center:yes;status:no;scroll:no;help:no;");
    }
    else {
        window.open(url, win, "top=" + iTop2 + ",left=" + iLeft2 + ",width=" + Width + "px,height=" + height2 + 
"px,resizable=0,scrollbars=0,location=0");
    }
}