关于各个浏览器的兼容问题

1.ie7中a标签的宽高与其父元素li不一样（现在浏览器中宽高是默认一样的）

方法：给a标签设置固定的宽、高

2.ie6以下对除了a之外的元素的hover不起作用等兼容问题

方法：

 body{
        behavior:url(csshover.htc);//引入该文件
      }

//csshover.htc源代码

<attach event="ondocumentready" handler="parseStylesheets"/> 
<script language="JScript"> 
var currentSheet, doc = window.document, activators = { 
onhover:{on:'onmouseover', off:'onmouseout'}, 
onactive:{on:'onmousedown', off:'onmouseup'} 
}; 
function parseStylesheets(){ 
var sheets = doc.styleSheets, l = sheets.length; 
for(var i = 0; i < l; i++){ 
parseStylesheet(sheets[i]); 
}; 
}; 
function parseStylesheet(sheet){ 
if(sheet.imports){ 
try{ 
var imports = sheet.imports, l = imports.length; 
for(var i = 0; i < l; i++){ 
parseStylesheet(sheet.imports[i]); 
}; 
}catch(securityException){}; 
}; 
try{ 
var rules = (currentSheet = sheet).rules, l = rules.length; 
for(var j = 0; j < l; j++){ 
parseCSSRule(rules[j]); 
}; 
}catch(securityException){}; 
}; 
function parseCSSRule(rule){ 
var select = rule.selectorText, style = rule.style.cssText; 
if(!(/(^|\s)(([^a]([^ ]+)?)|(a([^#.][^ ]+)+)):(hover|active)/i).test(select) || !style) return; 
var pseudo = select.replace(/[^:]+:([a-z-]+).*/i, 'on$1'); 
var newSelect = select.replace(/(\.([a-z0-9_-]+):[a-z]+)|(:[a-z]+)/gi, '.$2' + pseudo); 
var className = (/\.([a-z0-9_-]*on(hover|active))/i).exec(newSelect)[1]; 
var affected = select.replace(/:hover.*$/, ''); 
var elements = getElementsBySelect(affected); 
currentSheet.addRule(newSelect, style); 
for(var i = 0; i < elements.length; i++){ 
new HoverElement(elements[i], className, activators[pseudo]); 
}; 
}; 
function HoverElement(node, className, events){ 
if(!node.hovers) node.hovers = {}; 
if(node.hovers[className]) return; 
node.hovers[className] = true; 
node.attachEvent(events.on, function(){ 
node.className += ' ' + className; 
}); 
node.attachEvent(events.off, function(){ 
node.className = node.className.replace(new RegExp('\\s+'+className, 'g'),''); 
}); 
}; 
function getElementsBySelect(rule){ 
var parts, nodes = [doc]; 
parts = rule.split(' '); 
for(var i = 0; i < parts.length; i++){ 
nodes = getSelectedNodes(parts[i], nodes); 
}; 
return nodes; 
}; 
function getSelectedNodes(select, elements){ 
var result, node, nodes = []; 
var classname = (/\.([a-z0-9_-]+)/i).exec(select); 
var identify = (/\#([a-z0-9_-]+)/i).exec(select); 
var tagName = select.replace(/(\.|\#|\:)[a-z0-9_-]+/i, ''); 
for(var i = 0; i < elements.length; i++){ 
result = tagName ? elements[i].all.tags(tagName) : elements[i].all; 
for(var j = 0; j < result.length; j++){ 
node = result[j]; 
if((identify && node.id != identify[1]) || (classname && !(new RegExp('\\b' + classname[1] + '\\b').exec(node.className)))) continue; 
nodes[nodes.length] = node; 
}; 
}; 
return nodes; 
}; 
</script> 

3.检测ie6版本

//js兼容ie6
window.onload=function(){
    //判断是否为IE浏览器
    var isIE=!!window.ActiveXObject;
    var isIE6=isIE&&!window.XMLHttpRequest;
}
//Jquery兼容IE6
$(function(){
    if($.browser.msie&&$.browser.version.substr(0,1)<7){

    }
   //高版本的jquery检验ie6
   $.support.leadingWhitespace
})

4.