IE6下遮盖select，并解决页面滚动时，select闪烁问题
最近项目采用了jquery作为js库，easyui作为前提ui，但是它的的弹出宽遮罩没有解决IE6下select的穿透div层的问题，
进过讨论，决定采用iframe来覆盖select的方式解决。
用了iframe覆盖解决了传统问题，但是新的问题又出现了，如果页面有滚动条时，页面滚动的时候，被覆盖的select闪烁很厉害，页面停止了，闪烁也停止了，由于我们项目还采用了blockUI来自己弹出遮罩，发现blockUI也是采用iframe遮盖的方式：
// blockUI uses 3 layers for blocking, for simplicity they are all used on every platform;// layer1 is the iframe layer which is used to supress bleed through of underlying content// layer2 is the overlay layer which has opacity and a wait cursor (by default)// layer3 is the message content that is displayed while blockingvar lyr1 = ($.browser.msie || opts.forceIframe) ? $('<iframe style="z-index:'+ (z++) +';display:none;border:none;margin:0;padding:0;position:absolute;width:100%;height:100%;top:0;left:0" src="'+opts.iframeSrc+'"></iframe>'): $('<div style="display:none"></div>');var lyr2 = $('<div style="z-index:'+ (z++) +';display:none;border:none;margin:0;padding:0;width:100%;height:100%;top:0;left:0"></div>');var lyr3, s;if (opts.theme && full) {s = '<div style="z-index:'+z+';display:none;position:fixed">' +'<div style="z-index:'+z+';display:none;position:absolute">' +'<div style="z-index:'+z+';display:none;position:fixed"></div>';}else {s = '<div style="z-index:'+z+';display:none;position:absolute"></div>';}lyr3 = $(s);// simulate fixed position$.each([lyr1,lyr2,lyr3], function(i,o) {var s = o[0].style;s.position = 'absolute';if (i < 2) {full ? s.setExpression('height','Math.max(document.body.scrollHeight, document.body.offsetHeight) - (jQuery.boxModel?0:'+opts.quirksmodeOffsetHack+') + "px"') : s.setExpression('height','this.parentNode.offsetHeight + "px"');full ? s.setExpression('width','jQuery.boxModel && document.documentElement.clientWidth || document.body.clientWidth + "px"') : s.setExpression('width','this.parentNode.offsetWidth + "px"');if (fixL) s.setExpression('left', fixL);if (fixT) s.setExpression('top', fixT);}else if (opts.centerY) {if (full) s.setExpression('top','(document.documentElement.clientHeight || document.body.clientHeight) / 2 - (this.offsetHeight / 2) + (blah = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop) + "px"');s.marginTop = 0;}else if (!opts.centerY && full) {var top = (opts.css && opts.css.top) ? parseInt(opts.css.top) : 0;var expression = '((document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop) + '+top+') + "px"';s.setExpression('top',expression);}});state.mask.css({zIndex: $.fn.window.defaults.zIndex++,width: getPageArea().width,height: getPageArea().height,display: 'none'});<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>ieselect.html</title> </head> <body> <br> <br> <br> <br> <br> <br> <br> <br> <select id="sel1"></select> <br> <select id="sel2"></select> <iframe id="iframe" style="z-index:9000;display:none;border:0;width:100%;height:100%;position:absolute;"></iframe> <div id="div" style="z-index:9001;display:none;width:100%;height:100%;position:absolute;"></div> <button onclick="display();">display</button> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> <br> </body> <script type="text/javascript"> function $(id){ return document.getElementById(id); } function display(){ $('iframe').style.left = 0; $('iframe').style.top = 0; $('iframe').style.height = Math.max(document.body.scrollHeight, document.body.offsetHeight); $('iframe').style.display = 'block'; $('div').style.left = 0; $('div').style.top = 0; $('div').style.display = 'block'; $('div').style.setExpression('top', '(document.documentElement.clientHeight || document.body.clientHeight) / 2 - (this.offsetHeight / 2) + (blah = document.documentElement.scrollTop ? document.documentElement.scrollTop : document.body.scrollTop) + "px"'); } </script></html>