急救!!!!!!
<script>  
 function   changestyle(x) 
 { 
    for(var   i=1;i <=4;i++) 
       { 
             var   objx=eval( "s "+i);    
       	if(i==x) 
       	   { 
 		//document.getElementById( '+objx+ ').className= "on "; 
 		   objx.className= "on "; 
 	   } 
             else 
 		//document.getElementById( '+objx+ ').className= " "; 
 		objx.className= " "; 
       } 
    //   document.getElementById( 's2 ').className= "on "; 
 } 
  </script>  
  <div   class= "gNav ">  
  <ul   id= "ulTab ">  
 	 <li>  <a   href= "javascript:; "   class= "on "   onclick= "changestyle(1) "   id= "s1 "> 系统管理 </a>  </li>  
 		 <li>  <a   href= "javascript:; "   onclick= "changestyle(2) "   id= "s2 "> 产品管理 </a>  </li>  
 		 <li>  <a   href= "javascript:; "   onclick= "changestyle(3) "   id= "s3 "> 新闻管理 </a>  </li>  
 		 <li>  <a   href= "javascript:; "   onclick= "changestyle(4) "   id= "s4 "> 会员管理 </a>  </li>  
  </ul>  
  </div>      
 以上代码实现点击的时候改变连接的样式,使用objx.className= " ";可以,但是使用document.getElementById( '+objx+ ').className= " ";却不行,因为考虑到兼容火狐,所以要用第二种,也就是代码中注释掉的,getElementById中传参数不行,望高手指点!!!
------解决方案-------------------- <HTML>  
  <HEAD>  
  <META http-equiv= "Content-Type " content= "text/html; charset=gb2312 ">  
  <style>  
 .on{ 
 	background-color:red; 
 } 
  </style>  
  </HEAD>  
  <BODY>  
  <script>  
 function changestyle(x) 
 { 
  for(var i=1;i <=4;i++) 
   { 
   //  var objx=eval( "s "+i);  
 	var objx= "s "+i;  
   	if(i==x) 
   	 { 
 		document.getElementById(objx).className= "on "; 
 		// objx.className= "on "; 
 	 } 
     else 
 		document.getElementById(objx).className= " "; 
 		//objx.className= " "; 
   } 
  // document.getElementById( 's2 ').className= "on "; 
 } 
  </script>  
  <div class= "gNav ">  
  <ul id= "ulTab ">  
 	 <li>  <a href= "javascript:; " class= "on " onclick= "changestyle(1) " id= "s1 "> 系统管理 </a>  </li>  
 		 <li>  <a href= "javascript:; " onclick= "changestyle(2) " id= "s2 "> 产品管理 </a>  </li>  
 		 <li>  <a href= "javascript:; " onclick= "changestyle(3) " id= "s3 "> 新闻管理 </a>  </li>  
 		 <li>  <a href= "javascript:; " onclick= "changestyle(4) " id= "s4 "> 会员管理 </a>  </li>  
  </ul>  
  </div>  
  </BODY>  
  </HTML>