how to validate the E-mail ID....???

<asp:TextBox ID="TextBox1" runat="server" ToolTip="Enter your Email here">asp:TextBox>

<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" EnableViewState="False" Display="Static" ControlToValidate="TextBoxEmailId" ErrorMessage="Email must not be empty" SetFocusOnError="True"/> 

<asp:RegularExpressionValidator ID="RegularExpressionValidator1" Display="Static" runat="server" EnableViewState="False" ErrorMessage="Invalid Email" ControlToValidate="TextBoxEmailId"
ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*" SetFocusOnError="True"/>

<asp:Button ID="Button1" runat="server" Text="Check valid Email">asp:Button>

function ValidateForm() 
{
 if (document.getElementById('<%=txtMail.ClientID%>').value == "") 
 {
  alert("Please provide Email ID !");
  document.getElementById('<%=txtMail.ClientID%>').focus();
  return false;
 }
 else 
 {
  if (!(/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(document.getElementById('<%=txtMail.ClientID%>').value))) 
  {
   alert("The EmailId entered is not a valid Email Address. !");
   document.getElementById('<%=txtMail.ClientID%>').focus();
   return false;
  }
    }
}