CodingForums.com - Javascript validation problems

Hey guys, im a bit of a loser with Javascript and need a bit of validation done but I have no idea what the problem is with my code, can anyone help?

Form:
Code:
<div id="Layer3">

  <form id="form" name="form" method="post" onsubmit='return formValidator(form)' action="Candidate output.php">



    <p class="style3"><u>Search for a Candidate </u></p>

    <p class="style3">Candidate ID

      <input type="text" name="CandidateID" />

    </p>

    

<p class="style3">File

      <select name="File">

                   <option>--Select--</option>

                            <option>To be deleted</option>

    </p>



    <p class="style3">Name

      <input type="text" name="Name" />

    </p>



    <p class="style3">Current Job Title

      <select name="Current_Job_title">

                <option>--Select--</option>

                <option>Accessories</option>

      </select>

    </p>

    <p class="style3">Contact Telephone

      <input type="text" name="Contact_Telephone" />

    </p>



    <p class="style3">Contact Email

      <input type="text" name="Contact_Email" />



    </p>

    <p class="style3">Town

       <input type="text" name="Town" />

    </p>



    <p class="style3">County

      <select name="County">

                <option>--Select--</option>

                <option>Aberdeenshire</option>

         </select>

    </p>



    <p class="style3">Postcode

        <input type="text" name="Postcode" />

    </p>



    <p class="style3">Languages spoken

      <input type="text" name="Languages_Spoken" />

    </p>



    <p class="style3">Previous Job  Title

              <select name="Job_Title" >

                <option>--Select--</option>

                <option>Accessories</option>

        </select>

    </p>



    <p class="style3">Previous Employer

      <input type="text" name="Employer" />

    </p>



    <p class="style3">Previous Employment Type

      <select name="Employment_Type">

          <option>--Select--</option>

          <option>Manufacturer</option>

      </select>

    </p>



    <p class="style3">Previous Department Type

      <select name="Department_type">

            <option>--Select--</option>

                <option>Accounts</option>

      </select>

    </p>

        

    <p class="style3">Order By

      <select name="Order_By">

                  <option>--Select--</option>

                <option>CandidateID</option>

          </select>

 

        <input type="checkbox" name="Desc" value="y"  /> 

        Decending (Ascending leave unchecked)

        </p>

        

    <p class="style3">

              <input type="submit" name="Submit" value="Submit" />

    </p>



  </form>

</div>





Validation in the <Head>;



<script language="JavaScript" type='text/javascript'>



function formValidator(form){

        // Make quick references to our fields

        var CandidateID = document.getElementById('CandidateID');

        var Name = document.getElementById('Name');

        var Contact_T = document.getElementById('Contact_Telephone');

        var Contact_E = document.getElementById('Contact_Email');

        var Town = document.getElementById('Town');

        var Postcode = document.getElementById('Postcode');

        var Ls = document.getElementById('Languages_Spoken');

        var P_Employer = document.getElementById('Previous_Employer');

        

        /*http://www.tizag.com/javascriptT/javascriptform.php*/

        

        // Check each input in the order that it appears in the form!

        if(isNumeric(CandiateID, "Please enter numbers only")){

                if(isAlphabet(Name, "Please enter letters only")){

                        if(isNumeric(Contact_T, "Please enter numbers only")){

                                if(lengthrestriction(Contact_T, 11)){

                                        if(emailValidator(Contact_E, "Please enter a valid email address")){

                                                if(isAlphabet(Town, "Please enter letters only")){

                                                        if(postit(Postcode, "Please enter a valid Postcode")){

                                                                if(isAlphabet(LS, "Please enter letters only")){

                                                                        if(isAlphabet(P_Employer, "Please enter letters only")){

                                                                        return true;

                                                                        }

                                                                }

                                                        }

                                                }

                                        }

                                }

                        }

                }

        }

        

        

        return false;

        

function isNumeric(elem, alerttxt){

        var numericExpression = /^[0-9]+$/;

        if(elem.value.match(numericExpression)){

                return true;

        }else{

                alert(alerttxt);

                elem.focus();

                return false;

        }

}



function isAlphabet(elem, alerttxt){

        var alphaExp = /^[a-zA-Z]+$/;

        if(elem.value.match(alphaExp)){

                return true;

        }else{

                alert(alerttxt);

                elem.focus();

                return false;

        }

}



function isAlphanumeric(elem, alerttxt){

        var alphaExp = /^[0-9a-zA-Z]+$/;

        if(elem.value.match(alphaExp)){

                return true;

        }else{

                alert(alerttxt);

                elem.focus();

                return false;

        }

}



function lengthRestriction(elem, max){

        var uInput = elem.value;

        if(uInput.length >= uInput.length <= max){

                return true;

        }else{

                alert("Please enter between 0 and " +max+ " characters");

                elem.focus();

                return false;

        }

}



function emailValidator(elem, alerttxt){

        var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;

        if(elem.value.match(emailExp)){

                return true;

        }else{

                alert(alerttxt);

                elem.focus();

                return false;

        }

}



function postit(elem, alerttxt){ //check postcode format is valid

 test = document.details.Postcode.value; size = test.length

 test = test.toUpperCase(); //Change to uppercase

 while (test.slice(0,1) == " ") //Strip leading spaces

  {test = test.substr(1,size-1);size = test.length

  }

 while(test.slice(size-1,size)== " ") //Strip trailing spaces

  {test = test.substr(0,size-1);size = test.length

  }

 document.details.Postcode.value = test; //write back to form field

 if (size < 6 || size > 8){ //Code length rule

  alert(test + " is not a valid postcode - wrong length");

  document.details.Postcode.focus();

  return false;

  }

 if (!(isNaN(test.charAt(0)))){ //leftmost character must be alpha character rule

   alert(test + " is not a valid postcode - cannot start with a number");

   document.details.Postcode.focus();

   return false;

  }

 if (isNaN(test.charAt(size-3))){ //first character of inward code must be numeric rule

   alert(test + " is not a valid postcode - alpha character in wrong position");

   document.details.Postcode.focus();

   return false;

  }

 if (!(isNaN(test.charAt(size-2)))){ //second character of inward code must be alpha rule

   alert(test + " is not a valid postcode - number in wrong position");

   document.details.Postcode.focus();

   return false;

  }

 if (!(isNaN(test.charAt(size-1)))){ //third character of inward code must be alpha rule

   alert(test + " is not a valid postcode - number in wrong position");

   document.details.Postcode.focus();

   return false;

  }

 if (!(test.charAt(size-4) == " ")){//space in position length-3 rule

   alert(test + " is not a valid postcode - no space or space in wrong position");

   document.details.Postcode.focus();

   return false;

   }

 count1 = test.indexOf(" ");count2 = test.lastIndexOf(" ");

 if (count1 != count2){//only one space rule

   alert(test + " is not a valid postcode - only one space allowed");

   document.details.Postcode.focus();

   return false;

  }

alert("Postcode Format OK");

return true;

}



</script>
Im sure there are a few syntax errors but any and all help is greatly appreciated :)