<script language="javascript" type="text/javascript">         function textLimitCheck(thisArea, maxLength, SpanId)         {   if (thisArea.value.length > maxLength)             {                  thisArea.value = thisArea.value.substring(0, maxLength);                 thisArea.focus();             }             /*回写span的值，当前填写文字*/    var varss='（剩余字数：'+(maxLength-thisArea.value.length)+'）';        document.getElementById(SpanId).innerHTML =varss;         }     </script>

<asp:TextBox ID="txtOwner_Name" runat="server" Width="250px" MaxLength="50"  onkeyup="textLimitCheck(this,50,'spOwner_Name')" BackColor="Info"></asp:TextBox> <span id="spOwner_Name" style="color: gray"><em>（50字以内）</em></span>