Jquery issue while submitting the form

The problem what i am facing is when i click on the submit button in the form its not validating but directly posting to the php script while when i click on text boxes its validating perfectly i would need to validate the form before submission

Javascript Code

<script type="text/javascript">

                //Begin of Ready document
                $(document).ready(function () {

                        $("#fname").blur(function(){

                            if($("#fname").val() == "" ){

                                $("#fname").focus();
                                $("#fvalid").html("First Name Cannot be Blank");
                                return false;

                            }else{
                                $("#fvalid").html("");
                                return true;
                            }

                        });

                        $("#lname").blur(function(){

                            if($("#lname").val() == "" ){

                                $("#lname").focus();
                                $("#lvalid").html("Last Name Cannot be Blank");
                                return false;

                            }else{
                                $("#lvalid").html("");
                                return true;
                            }

                        });
</script>

HTML Code

<table class="content" cellspacing="0" cellpadding="0" align="center" style="padding-top:20px;">
                                <tr>
                                    <td class="contentfont">First Name<span class="sup">*</span></td>
                                    <td class="contentfont">:</td>
                                    <td><input type="textbox" name="fname" class="textbox" id="fname"></td>
                                </tr>
                                <tr>
                                    <td colspan="3"><span id="fvalid" class="failed"></span></td>
                                </tr>
                                <tr>
                                    <td class="contentfont">Last Name<span class="sup">*</span></td>
                                    <td class="contentfont">:</td>
                                    <td><input type="textbox" class="textbox" name="lname" id="lname"></td>
                                </tr>
                                <tr>
                                    <td colspan="3"><span id="lvalid" class="failed"></span></td>
                                </tr>
<tr>
                                <td align="center" colspan="3"><input type="submit" name="submit" class="register" value="Register Now" id="submit"></td>
                            </tr>

    <tr>
                                    <td align="center" colspan="3"><input type="submit" name="submit" class="register" value="Register Now" id="submit"></td>
                                </tr>

</table>

Can some one please help fix this