//选中当前导航
function selectNav(id){
    if(id=="nav_home"){
	     if(document.getElementById(id)!=null){
	          document.getElementById(id).className = "selected2";
	     }else{}
	}else{
		 if(document.getElementById(id)!=null){
	          document.getElementById(id).className = "selected";
	     }else{}
	}
}
function selectNav2(id){
    if(document.getElementById(id)!=null){document.getElementById(id).className = "selected";}else{}
}