function check_user_exists(form){
  uname=form.uname.value;
  pword=form.pword.value;
  typ=form.typ.value;
  if (uname==null||uname==''){
   alert("请输入用户名");
   return false;
  }
  if (pword==null||pword==''){
   alert("请输入密码");
   return false;
  }
  if (typ==null||typ==''){
   alert("请选择帐户类别");
   return false;
  }
  myurl=location.protocol+"//"+location.hostname+"/inc/chklogin.asp?typ="+typ+"&uname="+uname+"&pword="+pword;
  retCode=openUrl(myurl);
  switch(retCode){
   case "-2":
   alert("查询失败，请重试！");break;
   case "1":
   document.getElementById("emsg").innerHTML='会员中心<br><br>-'+uname+'-<br><br><a href=reg0.asp>[修改资料]</a><br><br><a href=bbs-search.asp?user='+uname+'>[我发布的贴子]</a><br><br><a href=logout.asp>[退出]</a>';break; 
   case "2":
   document.getElementById("emsg").innerHTML='-'+uname+'-<br><br><a href=mody.asp>[会员助手]</a><br><br><a href=regpro.asp>[添加产品]</a><br><br><a href=pjob.asp>[发布招聘信息]</a><br><br><a href=logout.asp>[退出]</a>';break;   case "0":
   case "0":
   alert("用户或密码无效！");break;
  }
  return;
 }

 function openUrl(url){
  var objxml=new ActiveXObject("Microsoft.XMLHttp")
  objxml.open("GET",url,false);  objxml.setRequestHeader("If-Modified-Since","0");
  objxml.send();
  retInfo=objxml.responseText;
  if (objxml.status=="200"){
   return retInfo;
  }
  else{
   return "-2";
  }
 }