Very beautiful way to make the background so dark (a method to change the background tone of the page when a prompt message pops up)_javascript skills

Someone asked about this effect on the forum a few days ago, and I had some time to study it today. I marked it as original because I did not refer to other people's code when writing this method. My method is actually layer masking and ALPHA filter to achieve the desired effect.

<meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>Prompt message box</title> <style type="text/css"> a{ color:#000; font-size:12px;text-decoration:none} a:hover{ color:#900; text-decoration:underline} body{background:;filter:progid:DXImageTransform.Microsoft.Gradient(gradientType=0,startColorStr=#ffffff,endColorStr=#003366); overflow:hidden} #massage_box{ position:absolute; left:expression((body.clientWidth-350)/2); top:expression((body.clientHeight-200)/2); width:350px; height:200px;filter:dropshadow(color=#666666,offx=3,offy=3,positive=2); z-index:2; visibility:hidden} #mask{ position:absolute; top:0; left:0; width:expression(body.clientWidth); height:expression(body.clientHeight); background:#666; filter:ALPHA(opacity=60); z-index:1; visibility:hidden} .massage{border:#036 solid; border-width:1 1 3 1; width:95%; height:95%; background:#fff; color:#036; font-size:12px; line-height:150%} .header{background:#036; height:10%; font-family:Verdana, Arial, Helvetica, sans-serif; font-size:12px; padding:3 5 0 5; color:#fff} </style> <div id="massage_box"><div class="massage"> <div class="header"> <div style="display:inline; width:150px; position:absolute">Prompt information from this site</div> <span onclick="massage_box.style.visibility='hidden'; mask.style.visibility='hidden'" style="float:right; display:inline; cursor:hand"></span> </div> </div></div>