html设置整个页面遮罩 简单遮罩 实现点击按钮遮住整个页面

通告";odiv.id = "div_whole";var styleStr = "filter: alpha(opacity=50); width:" + vis_x + "px; height:" + vis_y + "px; background-color: #F4F4F4; position:absolute; top:0px; left:0px;";odiv.style.cssText = styleStr;document.body.appendChild(odiv);document.getElementById("a").onclick = function () { document.getElementById("div_whole").style.display = "none";} } window.onresize = function () {showBox(); }