HELP!..cannot validate other elements of the form

<script language='javascript'>

function validate(){
var num=0;

document.getElementById('error_name').style.display='none';
document.getElementById('error_first_name').style.display='none';
document.getElementById('error_last_name').style.display='none';
document.getElementById('error_middle_name').style.display='none';
document.getElementById('error_province').style.display='none';
document.getElementById('error_country').style.display='none';
document.getElementById('error_street_add').style.display='none';
document.getElementById('error_zip_code').style.display='none';
document.getElementById('error_city').style.display='none';



if(document.getElementById('firstname').value=='' || document.getElementById('lastname').value=='' || document.getElementById('middlename').value==''){
    document.getElementById('error_name').style.display='block';
    num+=1;}

if(isName(document.getElementById('firstname').value)){
    document.getElementById('error_first_name').style.display='block';
    num+=1;}

if(isName(document.getElementById('lastname').value)){
    document.getElementById('error_last_name').style.display='block';
    num+=1;}

if(isName(document.getElementById('middleinitial').value) || (document.getElementById('middleinitial').value.length > 1) ){
    document.getElementById('error_middle_name').style.display='block';
    num+=1;}

if(document.getElementById('street').value==''){
    document.getElementById('error_street_add').style.display='block';
    num+=1;}

if((document.getElementById('zipcode').value=='') || isNumeric(document.getElementById('zipcode'))){
    document.getElementById('error_zip_code').style.display='block';
    num+=1;}
    
if((document.getElementById('city').value=='') || isName(document.getElementById('city').value)){
    document.getElementById('error_city').style.display='block';
    num+=1;}
    
if((document.getElementById('province').value=='') || isName(document.getElementById('province').value)){
    document.getElementById('error_province').style.display='block';
    num+=1;}
    
if(document.getElementById('country').value==''){
    document.getElementById('error_country').style.display='block';
    num+=1;}

    

if(num!=0 || x!=0){
    alert('The following field(s) is/are empty or invalid:\n\n'+num);
    num=0;
    return false;
}else    
    alert(num+' ' +x);
    
}
function isNumeric(elem){
    var numericExpression = /^[0-9]+$/;

    if(elem.value.match(numericExpression)){
        return false;
    }else{
        return true;
    }

}

function isName( value )
{
  if (/^[a-z]([a-z\s]*)$/i.test(value)==true)
    return false;
  else
    return true;
}
</script>

<form id="registration" name="registration" class="form1 page" autocomplete="off" enctype="multipart/form-data" method="post" onsubmit="return validate()" action="">
<ul>
    

<li id="foli0"         class="name   ">
    <label class="desc" id="title0" for="Field0">
        Name
        <span id="req_0" class="req">*</span>    
        <span class="req" id="error_name" style="display:none;"><em>Please complete your name</em></span>    
        <span class="req" id="error_first_name" style="display:none;"><em>Invalid first name</em></span>
        <span class="req" id="error_last_name" style="display:none;"><em>Invalid last name</em></span>
        <span class="req" id="error_middle_name" style="display:none;"><em>Invalid middle name</em></span>
            </label>
    
        <span>
        <input id="firstname"             name="firstname"             type="text"             class="field text"             value=""             size="20"             tabindex="1"         onFocus="this.value=''"                />
        <label for="Field1">First</label>
    </span>
    <span>
        <input id="lastname"             name="lastname"             type="text"             class="field text"             value=""             size="20"             tabindex="2"         onFocus="this.value=''"                />
        <label for="Field2">Last</label>
    </span>
    <span>
        <input             name="middleinitial"             type="text"             class="field text" id="middleinitial"             tabindex="3"             value=""             size="3"     onFocus="this.value=''"                    />
        <label for="Field3">MI</label>
    </span>    </li></ul></form>