how can i use my javascript function in my html form

<script type='text/javascript'>

function formValidator(){
	// Make quick references to our fields
	var pname = document.getElementById('pname');
	var address = document.getElementById('address');
	var contact = document.getElementById('contact');
	var email = document.getElementById('email');
	var subject = document.getElementById('subject');
	var comments = document.getElementById('comments');
	
	// Check each input in the order that it appears in the form!
	if(isAlphabet(pname, "Please enter only letters for your name")){
		if(isAlphanumeric(address, "Numbers and Letters Only for Address")){
			if(isNumeric(contact, "Please enter a valid COntact Number")){
				if(emailValidator(email, "Please enter a valid email address")){
					if(isAlphabet(subject, 25, 50)){
						if(isAlphanumeric(comments, "Your are entering to much words in comments")){
							return true;
						}
					}
				}
			}
		}
	}
	
	
	return false;
	
}

function notEmpty(elem, helperMsg){
	if(elem.value.length == 0){
		alert(helperMsg);
		elem.focus(); // set the focus to this input
		return false;
	}
	return true;
}

function isNumeric(elem, helperMsg){
	var numericExpression = /^[0-9]+$/;
	if(elem.value.match(numericExpression)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphabet(elem, helperMsg){
	var alphaExp = /^[a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function isAlphanumeric(elem, helperMsg){
	var alphaExp = /^[0-9a-zA-Z]+$/;
	if(elem.value.match(alphaExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}

function lengthRestriction(elem, min, max){
	var uInput = elem.value;
	if(uInput.length >= min && uInput.length <= max){
		return true;
	}else{
		alert("Please enter between " +min+ " and " +max+ " characters");
		elem.focus();
		return false;
	}
}


function emailValidator(elem, helperMsg){
	var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
	if(elem.value.match(emailExp)){
		return true;
	}else{
		alert(helperMsg);
		elem.focus();
		return false;
	}
}
</script>

<tr>

                            <td class="text7">*</td>

                            <td class="text4">Name</td>

                            <td class="blacktext11"><input name="pname"  type="text" class="border2"  style="width: 180px;" /></td>

                          </tr>

                          <tr>

                            <td valign="top" class="text7">*</td>

                            <td class="text4" valign="top">Address</td>

                            <td class="blacktext11"><textarea name="address" cols="20" rows="2" class="border2"  style="width: 180px;" ></textarea></td>

                          </tr>

                          <tr>

                            <td class="text7">*</td>

                            <td class="text4">Contact Number</td>

                            <td class="blacktext11" valign="top"><input name="contact"  type="text" class="border2"  style="width: 180px;" /></td>

                          </tr>

                          <tr>

                            <td class="text7">*</td>

                            <td class="text4">Email Address</td>

                            <td class="blacktext11" valign="top"><input name="email" class="border2" style="width: 180px;"  type="text" /></td>

                          </tr>

                          <tr>

                            <td class="text7">*</td>

                            <td class="text4">Subject</td>

                            <td class="blacktext11" valign="top"><input name="subject" class="border2" style="width: 180px;" type="text" /></td>

                          </tr>

                          <tr>

                            <td class="text7">*</td>

                            <td class="text4">Comments</td>

                            <td class="blacktext11" valign="top"><textarea cols="20" rows="2" name="comments" class="border2" style="width: 180px;"></textarea></td>

                          </tr>
</form>


                          <tr>

                            <td> </td>

                            <td> </td>

                            <td style="text-align: left;" align="left"><input name="submit"  value="Submit" style="width: 60px; font-family:Arial, Helvetica, sans-serif; font-size:12px; color:#FFFFFF; font-weight:bold; border:1px solid #CCCCCC; background-color:#000000;" type="submit" />
</td></tr>