点击按钮后，弹出一个可关闭的层窗口，随之网页背景变灰，在QQ网站上经常会看到QQ登录的效果，就和这个很类似，代码段基于JavaScript，根据你的情况使用，有时候是用CSS完成的这种功能。
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>弹出一个层，页面变灰</title><mce:script language="javascript"><!--function alertWin(title, msg, w, h){ var titleheight = "23px"; // 窗口标题高度 var bordercolor = "#336699"; // 提示窗口的边框颜色 var titlecolor = "#FFFFFF"; // 窗口标题颜色 var titlebgcolor = "#336699"; // 窗口标题背景色var bgcolor = "#FFFFFF"; // 提示内容的背景色var iWidth = document.documentElement.clientWidth; var iHeight = document.documentElement.clientHeight; var bgObj = document.createElement("div"); bgObj.style.cssText = "position:absolute;left:0px;top:0px;width:"+iWidth+"px;height:"+Math.max(document.body.clientHeight, iHeight)+"px;filter:Alpha(Opacity=30);opacity:0.3;background-color:#000000;z-index:101;";document.body.appendChild(bgObj); var msgObj=document.createElement("div");msgObj.style.cssText = "position:absolute;font:11px '宋体';top:"+(iHeight-h)/2+"px;left:"+(iWidth-w)/2+"px;width:"+w+"px;height:"+h+"px;text-align:center;border:1px solid "+bordercolor+";background-color:"+bgcolor+";padding:1px;line-height:22px;z-index:102;";document.body.appendChild(msgObj);var table = document.createElement("table");msgObj.appendChild(table);table.style.cssText = "margin:0px;border:0px;padding:0px;";table.cellSpacing = 0;var tr = table.insertRow(-1);var titleBar = tr.insertCell(-1);titleBar.style.cssText = "width:100%;height:"+titleheight+"px;text-align:left;padding:3px;margin:0px;font:bold 13px '宋体';color:"+titlecolor+";border:1px solid " + bordercolor + ";cursor:move;background-color:" + titlebgcolor;titleBar.style.paddingLeft = "10px";titleBar.innerHTML = title;var moveX = 0;var moveY = 0;var moveTop = 0;var moveLeft = 0;var moveable = false;var docMouseMoveEvent = document.onmousemove;var docMouseUpEvent = document.onmouseup;titleBar.onmousedown = function() {var evt = getEvent();moveable = true; moveX = evt.clientX;moveY = evt.clientY;moveTop = parseInt(msgObj.style.top);moveLeft = parseInt(msgObj.style.left);document.onmousemove = function() {if (moveable) {var evt = getEvent();var x = moveLeft + evt.clientX - moveX;var y = moveTop + evt.clientY - moveY;if ( x > 0 &&( x + w < iWidth) && y > 0 && (y + h < iHeight) ) {msgObj.style.left = x + "px";msgObj.style.top = y + "px";}}};document.onmouseup = function () { if (moveable) { document.onmousemove = docMouseMoveEvent;document.onmouseup = docMouseUpEvent;moveable = false; moveX = 0;moveY = 0;moveTop = 0;moveLeft = 0;} };}var closeBtn = tr.insertCell(-1);closeBtn.style.cssText = "cursor:pointer; padding:2px;background-color:" + titlebgcolor;closeBtn.innerHTML = "<span style="font-size:15pt; color:"+titlecolor+";" mce_style="font-size:15pt; color:"+titlecolor+";">×</span>";closeBtn.onclick = function(){ document.body.removeChild(bgObj); document.body.removeChild(msgObj); } var msgBox = table.insertRow(-1).insertCell(-1);msgBox.style.cssText = "font:10pt '宋体';";msgBox.colSpan = 2;msgBox.innerHTML = msg;// 获得Event对象，用于兼容IE和FireFoxfunction getEvent() {return window.event || arguments.callee.caller.arguments[0];}} // --></mce:script></head><body><input type="button" value="点这里" οnclick="alertWin('kissMe','KissMe And LoveMe',290,208);" /></body></html>
