Javascript Form Validation, Lots of work: 365 programming project day thirty three

<form name="f" method="post" action="send_enquiry_displays.asp">
    <td nowrap>First Name:*  </td>

    <td><input class="pTextBox1" name="txFirstName" type="text" value=""></td>

    More form stuff here...  Notice that the radio button only has one choice...

    <input type="radio" name="rdDisplaySize" value="5.7 VGA TFT"></td>

    <td nowrap>Wireless LAN:  </td>
    <td><input type="checkbox" name="ckWirelessLAN" value="1"></td>

    <td valign="top"><input type="hidden" name="whereDidYouHear" value="WUNL0309#1"></td>

    <td><a href="javascript:checkSingupForm()" onClick="this.blur()"

    onmouseover="genericRollover('elImgSubmit','images/buttons/submit_over.gif');
    window.status='Submit Form';return true;"

    onmouseout="genericRollover('elImgSubmit','images/buttons/submit.gif');
    window.status='';return true;">

    <img src="images/buttons/submit.gif" name="elImgSubmit"
    alt="Submit Form" width="66" height="22" hspace="10" border="0">
    </a></td>

    </table>
    </td>
    </tr>
</form>

<script language="JavaScript">

function checkSingupForm(){
    var f = document.forms["f"];

    //this array should contain every text field you require to be filled in
        var arr = [
                     ["txFirstName","First Name"]
                    ,["txLastName","Last Name"]
                    ,["txCompany","Company"]
                    ,["txTown","Town"]
                ,["txEmail","E-mail"]
    ];

    //for loop checks each value if it is blank "" ... then popup alert and changes focus
    for(i=0;i<arr.length;i++){
        if(f.elements[arr[i][0]].value == ""){
            alert("Please fill in " + arr[i][1] + ".")
            f.elements[arr[i][0]].focus();
            return;
        }
    }

    //a regular expression check to ensure the email is in a valid email format
    var emailRE = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9_\-])+\.)+([a-zA-Z0-9]{2,4})+$/
    if( !emailRE.exec(f.elements["txEmail"].value) ){
        alert("Please fill in a valid e-mail address.");
        f.elements["txEmail"].focus();
        return;
    }

    //ensures that the display size have been filled out...

    rdDisplaySizeValid = -1;
    for( i=0; i< f.elements["rdDisplaySize"].length; i++)
    {
        if( f.elements["rdDisplaySize"][i].checked )
        {   
            rdDisplaySizeValid = 1; 
        }
    }

    if( rdDisplaySizeValid == -1 )
    {
        alert("Please choose a Display size.");
        f.elements["rdDisplaySize"][0].focus();
        return;
    }

    //ensures that the embeddedconfiguration field has been checked at least once...
    if(!f.elements["rdEmbeddedConfiguration"][0].checked && !f.elements["rdEmbeddedConfiguration"][1].checked) 
    {
        alert("Please choose a Embedded Configuration.");
        f.elements["rdEmbeddedConfiguration"][0].focus();
        return;
    }

    f.submit();
}

//-->
</script>