Script
<script type="text/javascript">
$(document).ready(function () {
$('.isFloat').keypress(function(event) {
if ((event.which != 46 || $(this).val().indexOf('.') != -1) && (event.which < 48 || event.which > 57)) {
event.preventDefault();
}
});
});
</script>
<asp:TextBox ID="txtTotlaMark" runat="server" pattern="^[0-9 .]{1,}$" class="isFloat" MaxLength="6" required></asp:TextBox>