<script language="vbscript">
function ValidateEmail(sEmail)
    set myExpression = new RegExp
    myExpression.pattern = "^(\w+\.)*(\w+)@(\w+\.)+([a-zA-Z]{2,4})$"
    If myExpression.test(sEmail.value) = True Then
	msgbox "Valid Email"
    Else
	msgbox "Invalid Email"
    End If
End Function
</script>

<form name="email">
<input type=text name="txtEmail" maxlength=44 width=40>
<input type=button onclick="ValidateEmail(txtEmail)">
</form>