//得到地址参数值
function getUrl(url, paramname)   
{   
 var reg = new RegExp("(^|\\?|&)"+ paramname +"=([^&]*)(\\s|&|$)", "i");     
 if (reg.test(url)) return RegExp.$2; return "";   
}
//更改地址参数值
function EditUrl(oldurl,paramname,pvalue){   
 var reg = new RegExp("(\\?|&)"+ paramname +"=([^&]*)(&|$)","gi");   
 var t=oldurl.match(reg)[0];   
 var retxt=t.substring(0,t.indexOf("=")+1)+pvalue;   
 if(t.charAt(t.length-1)=='&') retxt+="&";   
 return oldurl.replace(reg,retxt);   
 }