u can remove space by using function trim which is not in javascript

u can remove space by using function trim which is not in javascript

  function trim(str, chars)
  {
      return ltrim(rtrim(str, chars), chars);
  }

  function ltrim(str, chars)
  {
      chars = chars || "\\s";
      return str.replace(new RegExp("^[" + chars + "]+", "g"), "");
  }

  function rtrim(str, chars)
  {
      chars = chars || "\\s";
      return str.replace(new RegExp("[" + chars + "]+$", "g"), "");
  }
  
  
  
     function Validate()
     {
       if (trim(document.getElementById("txtReason").value,' ')=="")
       {
       alert("Please enter the cancellation reason");
       return false;
       }
       return true;
      
     }

html for page will be

<asp:TextBox id="txtReason" Runat="server" onkeypress="doKeypress(this);" onbeforepaste="doBeforePaste(this);"
onpaste="doPaste(this);" Width="256px" MaxLength="200" TextMode="MultiLine" Height="98px"></asp:TextBox>
<asp:requiredfieldvalidator id="RequiredFieldValidator1" runat="server" CssClass="errormessage" ForeColor=" "
ErrorMessage="Please enter reason" Display="Dynamic" ControlToValidate="txtReason">