FCK的长度限制

<script language="javascript">
      /*验证*/
      function ClientValidate()
   {      
    if(document.getElementById('t_title').value=="")
       {
     alert('帖子标题为必填项,请填写!');
     return false;
       }
    if(parseInt(GetMessageLength("txtbody"))>10)   
    {       
     alert('帖子内容的最大长度为4000,请分段发贴!');  
     alert(parseInt(GetMessageLength("txtbody")));            
     return false;   
    }
   }
   function GetMessageLength(str)
   {   
    var oEditor = FCKeditorAPI.GetInstance(str) ;
    var oDOM = oEditor.EditorDocument ;
    var iLength ;
    if ( document.all )        // If Internet Explorer.   
    {      
         iLength = oDOM.body.innerHTML.length ;  //innerText.length ;
       }   
    else                    // If Gecko.   
    {    var r = oDOM.createRange() ;
         r.selectNodeContents( oDOM.body ) ;
         iLength = r.toString().length ;   
    }
    //oEditor.InsertHtml('')
    return iLength
            }
          
   function tagschange()
   {
       if(document.getElementById("DropDownList1").options[document.getElementById("DropDownList1").selectedIndex].value!=0)
       {
           if(document.getElementById("tags").value.split(',').length<=2)
     {    
      if(document.getElementById("tags").value=="")
      {
       document.getElementById("tags").value=document.getElementById("DropDownList1").options[document.getElementById("DropDownList1").selectedIndex].text;
      }
      else
      {
       document.getElementById("tags").value+=","+document.getElementById("DropDownList1").options[document.getElementById("DropDownList1").selectedIndex].text;
      }
     }
     else
     {
      alert('最多选择三个标签!');
     }
       }
   }
   function tagsclear()
   {
       document.getElementById("tags").value="";      
   }   
  </script>