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How can I prevent my form from being submitted?

I want the form to not be submitted when the inputs are wrong. The error messages do appear but my form still gets submitted nonetheless. I cant seem to find the problem would appreciate the help thank you :)-----------------------------------------------------------------------------------------------------
<form action="/handleServer.php" method="get" onsubmit="return validateForm()">
<!-- starting with first name-->
<h4 class="heading" >First name:</h4>
<input id="fname" type="text" name="fname" size="30">
<span id="errorName" class="error"></span>
<!-- module code -->
<h4 class="heading">Module code:</h4>
<input id="mcode" type="text" name="mcode" size="30">
<span id="errorCode" class="error"></span>
<input type="submit" value="Submit">
</form>
<script>
//input field using if-else statements
function validateForm() {
var fname = document.getElementById("fname").value;
var mcode = document.getElementById("mcode").value;
var errorN = document.getElementById("errorName");
var errorC = document.getElementById("errorCode");
//test for an empty input
if (fname === '' && mcode === '') {
errorN.innerHTML = "Please fill in the blank";
errorC.innerHTML = "Please fill in the blank";
return false;
}
if (fname === '') {
errorN.innerHTML = "Please fill in the blank";
return false;
} else {
errorN.innerHTML = "";
}
if (mcode === '') {
errorC.innerHTML = "Please fill in the blank";
return false;
} else {
errorC.innerHTML = "";
}
//test for invalid format
if (/^[A-Z]\D{2,30}$/.test(fname) == false) //if its true, it will go to the second input
{
errorN.innerHTML = "One capital letter and no digits allowed";
fname.style.color="red";
return false;
} else {
fname.innerHTML = "";
}
if (/^[a-z]{3}[1-9]\d{4}$/.test(mcode) == false)
{
errorC.innerHTML = "Wrong format";
mcode.style.color="red";
return false;
} else {
mcode.innerHTML = "";
}
return true; }

The problem seems to be these four lines of code:
fname.style.color="red";
fname.innerHTML = "";
mname.style.color="red";
mname.innerHTML = "";
fname and mname are strings, therfore fname.style and mname.style both result in undefined. Obviously you can't set properties on undefined which is why you are getting an error.
//You are getting the value properties which are strings:
var fname = document.getElementById("fname").value;
var mcode = document.getElementById("mcode").value;
The error is stopping your code before you can return false, preventing the cancelation of the form submit.
The solution is to instead make two more variables storing the actual input elements:
var finput = document.getElementById("fname");
var minput = document.getElementById("mname");
Then change lines:
fname.style.color="red";
fname.innerHTML = "";
mname.style.color="red";
mname.innerHTML = "";
to:
finput.style.color="red";
finput.innerHTML = "";
minput.style.color="red";
minput.innerHTML = "";
Here is a working version:
<form action="/handleServer.php" method="get" onsubmit="return validateForm()">
<!-- starting with first name-->
<h4 class="heading">First name:</h4>
<input id="fname" type="text" name="fname" size="30">
<span id="errorName" class="error"></span>
<!-- module code -->
<h4 class="heading">Module code:</h4>
<input id="mcode" type="text" name="mcode" size="30">
<span id="errorCode" class="error"></span>
<input type="submit" value="Submit">
</form>
<script>
//input field using if-else statements
function validateForm() {
var finput = document.getElementById("fname");
var minput = document.getElementById("mname");
var fname = document.getElementById("fname").value;
var mcode = document.getElementById("mcode").value;
var errorN = document.getElementById("errorName");
var errorC = document.getElementById("errorCode");
//test for an empty input
if (fname === '' && mcode === '') {
errorN.innerHTML = "Please fill in the blank";
errorC.innerHTML = "Please fill in the blank";
return false;
}
if (fname === '') {
errorN.innerHTML = "Please fill in the blank";
return false;
} else {
errorN.innerHTML = "";
}
if (mcode === '') {
errorC.innerHTML = "Please fill in the blank";
return false;
} else {
errorC.innerHTML = "";
}
//test for invalid format
if (/^[A-Z]\D{2,30}$/.test(fname) == false) //if its true, it will go to the second input
{
errorN.innerHTML = "One capital letter and no digits allowed";
finput.style.color = "red";
return false;
} else {
finput.innerHTML = "";
}
if (/^[a-z]{3}[1-9]\d{4}$/.test(mcode) == false) {
errorC.innerHTML = "Wrong format";
minput.style.color = "red";
return false;
} else {
minput.innerHTML = "";
}
return true;
}
</script>

Pass the event to the form validation function
onsubmit="return validateForm(e)"
Then prevent default submission using
e.preventDefault();

Your return statement should be inside a condition. Right now you're existing the condition and ending the function with a return true; regardless of what the conditional statements have already returned. So:
if (fname === '' && mcode === '') {
errorN.innerHTML = "Please fill in the blank";
errorC.innerHTML = "Please fill in the blank";
return false;
}else{
return true; // THIS IS WHERE YOU NEED TO RETURN TRUE
}
I see you're returning false in multiple if statements. You'll need to find a way to unify the conditions so that you have one return only for for either true or false.

Partial validation executed

I am trying to do few validations in a form and it is not up to the mark. I need to hide the error message message of the name and show only email error. But it is not happening. Maybe you will understand from the code.
Here it is.
function validateform(form){
event.preventDefault();
console.log(form);
var i;
var fname = form.name.value;
var email = form.email.value;
var message = form.getElementsByClassName("error-message");
var atpos = email.indexOf("#");
var dotpos = email.lastIndexOf(".");
if (fname==null || fname==""){
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-message")[i].innerHTML="Please Enter Name";
return false;
}
}
else if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) {
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-email")[i].innerHTML="The email address you've entered contains an incorrect character. Please check this information and try again.";
return false;
}
}
else if (fname!=null || fname!=""){
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-message")[i].style.display = "none";
return false;
}
}
HTML
<form name="ccform" method="post" onsubmit="validateform(this)">
<p class="customer-name">Name</p>
<input type="text" class="input-name" name="name"></input>
<p class="error-message"></p>
<p class="customer-name">Email</p>
<input type="text" class="input-name" name="email" placeholder="e.g. name#emailaddress.com"></input>
<p class="error-email"></p>
<button type="submit" class="submit-button">Submit</button>
</form>
I want to hide error-message and show only error-email when name is entered,email is not entered and i press submit button.
P.S: Please no jQuery.

You have trying to hide error_message class in an else if condition. The code will not parse through all the if conditions. In your case, you want to show the email validation message and hence it will enter the second condition and will not enter the third condition. Refer the usage of if-else if-else statement here. You just try to merge the second and third condition together as follows.
if (fname==null || fname==""){
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-message")[i].innerHTML="Please Enter Name";
form.getElementsByClassName("error-message")[i].style.display = "block";
return false;
}
} else {
form.getElementsByClassName("error-message")[i].style.display = "none";
}
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) {
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-email")[i].innerHTML="The email address you've entered contains an incorrect character. Please check this information and try again.";
form.getElementsByClassName("error-email")[i].style.display = "block";
return false;
}
} else {
form.getElementsByClassName("error-email")[i].style.display = "none";
}
Hope it helps.

This is what worked for me.
function validateform(form){
var i;
var fname = form.name.value;
var email = form.email.value;
var message = form.getElementsByClassName("error-message");
var atpos = email.indexOf("#");
var dotpos = email.lastIndexOf(".");
if (fname==null || fname==""){
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-message")[i].innerHTML="Please enter your name";
form.getElementsByClassName("error-message")[i].style.display = "block";
form.getElementsByClassName("error-email")[i].style.display = "none";
return false;
}
}
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=email.length) {
for (i = 0; i < message.length;i++)
{
form.getElementsByClassName("error-email")[i].innerHTML="The email address you've entered contains an incorrect character. Please check this information and try again.";
form.getElementsByClassName("error-message")[i].style.display = "none";
form.getElementsByClassName("error-email")[i].style.display = "block";
return false;
}
}

Request to server fails in Firefox when type=submit for button

My html code sends the request to php to send email. In my case the email can be sent in Google Chrome & Edge but not in Firefox when I set the button type=submit, when I change type=button, it works fine. My javascript code is:
function Send() {
var allset = true;
var namevalid = true;
var emailvalid = false;
var commentvalid = false;
var sent = 0;
var emailPattern = /^[a-zA-Z0-9._-]+#[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;
if ($("#email").val() == '' || $("#email").val() == null) {
$("#email").addClass("invalid");
allset = false;
}
else {
if (!$("#email").val().match(emailPattern)) {
$("#email").removeClass("valid");
$("#email").addClass("invalid");
allset = false;
}
else {
emailvalid = true;
$("#email").addClass("valid");
}
}
if ($("#comment").val() == '' || $("#comment").val() == null) {
$("#comment").addClass("invalid");
allset = false;
}
else {
commentvalid = true;
$("#comment").addClass("valid");
}
$("#name").addClass("valid");
if (namevalid === true && emailvalid === true && commentvalid === true) {
var name = document.getElementById("name").value;
var email = document.getElementById("email").value;
var number = document.getElementById("number").value;
var demo = document.getElementById("sel1").value;
var comment = document.getElementById("comment").value;
alert("Request Successfully Received");
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function () {
if (xhttp.readyState == 4 && xhttp.status == 200) {
alert(xhttp.responseText)
}
};
sent = 1;
xhttp.open("POST", "email.php?" + "name=" + name + "&mail=" + email + "&phone=" + number + "&msg=" + comment + "&demo=" + demo, true);
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhttp.send();
}
else
{
alert("Please fill all the fields correctly");
}
}
My html for form's button is:
<form class="form" id="form1">
<p class="name">
<input name="name" type="text" class="validate[required,custom[onlyLetter],length[0,100]] feedback-input" placeholder="Name" id="name" />
</p>
<p class="email">
<input name="email" type="text" class="validate[required,custom[email]] feedback-input" id="email" placeholder="Email" />
</p>
<p class="number">
<input type="text" name="telephone" maxlength="30" class="feedback-input" size="30" id="number" placeholder="Number">
</p>
<p class="number" id="demotype">
<select class="form-control feedback-input demotype" id="sel1" name="demo">
<option> something </option>
</select>
</p>
<p class="text">
<textarea name="text" class="validate[required,length[6,300]] feedback-input" id="comment" placeholder="Comment"></textarea>
</p>
<div class="submit">
<input type="submit" id="button-blue" onclick="Send()" value="Send" />
<div class="ease"></div>
</div>
</form>

'type=submit' is basically for submitting forms and 'type=button' is just a button to be bind with some functions. If you don't have any form as its parent element and an error occurs when you click the button, I suggest you to use 'type=button' instead.

Just add return false; at the end of function becuase submit button submits your form. Like this.
function Send() {
var allset = true;
var namevalid = true;
var emailvalid = false;
var commentvalid = false;
var sent=0;
var emailPattern = /^[a-zA-Z0-9._-]+#[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}$/;
if ($("#email").val() == '' || $("#email").val() == null) {
$("#email").addClass("invalid");
allset = false;
}
else {
if (!$("#email").val().match(emailPattern)) {
$("#email").removeClass("valid");
$("#email").addClass("invalid");
allset = false;
}
else {
emailvalid = true;
$("#email").addClass("valid");
}
}
if ($("#comment").val() == '' || $("#comment").val() == null) {
$("#comment").addClass("invalid");
allset = false;
}
else {
commentvalid = true;
$("#comment").addClass("valid");
}
$("#name").addClass("valid");
if (namevalid === true && emailvalid === true && commentvalid === true) {
var name = document.getElementById("name").value;
var email = document.getElementById("email").value;
var number = document.getElementById("number").value;
var demo=document.getElementById("sel1").value;
var comment = document.getElementById("comment").value;
alert("Request Successfully Received");
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (xhttp.readyState == 4 && xhttp.status == 200) {
alert(xhttp.responseText)
}
};
sent=1;
xhttp.open("POST", "email.php?"+"name="+name+"&mail="+email+"&phone="+number+"&msg="+comment+"&demo="+demo, true);
xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhttp.send();
}
else
{
alert("Please fill all the fields correctly");
}
return false;
}

Problems with form validations

<div id="form">
<form method="post" action="register1.aspx" onsubmit="return validateForm();"name="register1" >
<h1>
Register to exess the site</h1>
<input type="text" name="firstname" class=" br"/>
<em>First name</em><br />
<span id="firstnmsg"></span><br />
<input type="text" name="lastname" class=" br" /><em>Last name</em><br />
<span id="lastnmsg"></span><br />
<input type="text" name="username" class=" br" /><em>username</em><br>
<span id="usermsg"></span><br />
<input type="password" name="password" class=" br" /><em>password</em><br />
<input type="password"name="password1" class=" br" /><em>Confirm password</em>
<span id="pass1msg"></span><br />
<input type="text" name="email" class=" br"/><em>Email!</em><br />
<span id="emailmsg"></span><br />
<select name="sex">
<option>Please select a Gender</option>
<option>Male</option>
<option>Female</option>
<em>Gender</em>
</select><br />
<input type="submit" name="submit" value="Register " onclick="return validateForm();" />
<input type="reset" name="reset" value="Reset" onclick="return resetMsg();"/>
</form>
<span> <%=Session["regstatus"] %></span>
</div>
<div id="log_in">
<h1><em>log in</em></h1>
<form action="WebForm2.aspx"method="post" name="log_in" onsubmit="return validateloginform"><br />
<span id="usernamemsg"><%=Session["usernamemsg"] %> </span><input type="text" name="username_1" class="br" /><em>Username</em><br />
<span id="passwordmsg"><%=Session ["passwordmsg"] %></span><input type="password" name="password_1" class="br" /><em>Password</em><br />
<input type="submit" name="submit2" onclick=" validateloginform"/>
</form>
</div>
<script type="text/javascript">
function isEmpty(str) {
return (str.length == 0);
}
function isNumeric(str) {
var c = true;
for (var i = 0; i < str.length; i++) {
c = !(isNaN(str[i]));
}
return c;
}
function isValid(str) {
var badChar = "\\;:!##$%^&*()-_=+`~<>?[]{}|/,.";
for (var l = 0; l < str.length; l++) {
for (var c = 0; c < badChar.length; c++) {
if (str[l] == badChar[c]) {
return true;
}
if (str[l] == " " || str[l] == "\"" || str[l] == "\'") {
return true;
}
}
}
return false;
}
function isShort(str) {
return (str.length < 3);
}
//Reset Error Messages Function -->
function resetMsg() {
document.getElementById("firstnmsg").innerHTML = "";
document.getElementById("lastnmsg").innerHTML = "";
document.getElementById("usermsg").innerHTML = "";
document.getElementById("passwordmsg").innerHTML = "";
document.getElementById("pssword1msg").innerHTML = "";
document.getElementById("emailmsg").innerHTML = "";
document.getElementById("BdateMsg").innerHTML = "";
document.getElementById("UnameMsg").innerHTML = "";
document.getElementById("PwdMsg").innerHTML = "";
document.getElementById("LoginError").innerHTML = "";
return true;
}
//Main Sign Up Form Validation Function -->
function validateForm() {
resetMsg();
var val = true;
//First Name Validation ---------------------------------------->
if (isEmpty(register1.firstname.value)) {
document.getElementById("firstnmsg").innerHTML = " Empty";
val = false;
}
else {
if (isNumeric(register1.firstname.value) || isValid(signup.firstname.value)) {
document.getElementById("firstnmsg").innerHTML = " Letters Only";
val = false;
}
else {
if (isShort(register1.firstname.value)) {
document.getElementById("firstnmsg").innerHTML = " Too Short";
val = false;
}
}
}
//Last Name Validation ------------------>
if (isEmpty(register1.lastname.value)) {
document.getElementById("lastnmsg").innerHTML = " Empty";
val = false;
}
else {
if (isNumeric(register1.lastname.value) || isValid(signup.lastname.value)) {
document.getElementById("lastnmsg").innerHTML = " Letters Only";
val = false;
}
else {
if (isShort(register1.lastname.value)) {
document.getElementById("lastnmsg").innerHTML = " Too Short";
val = false;
}
}
}
//Username Validation --------------------------------------------->
if (isEmpty(register1.username.value)) {
document.getElementById("usermsg").innerHTML = " Empty";
val = false;
}
else {
if (!isNumeric(register1.username.value)) {
document.getElementById("usermsg").innerHTML = " Use Numbers";
}
else {
if (isShort(register1.username.value)) {
document.getElementById("usermsg").innerHTML = " Too Short";
val = false;
}
}
}
//Password Validation ----------------------------------------------->
if (isEmpty(register1.password1.value)) {
document.getElementById("Password1Msg").innerHTML = " Empty";
val = false;
}
else {
if (isValid(register1.password.value)) {
document.getElementById("Password1Msg").innerHTML = " Invalid";
}
else {
if (register1.password.value == register1.password1.value) {
if (signup.password1.value.length < 6 && signup.password1.value != "") {
document.getElementById("pass1msg").innerHTML = " Too Short";
val = false;
}
}
else {
document.getElementById("pass1msg").innerHTML = " Don't Match";
val = false;
}
}
}
//Email Validation -------------------------------------->
var EmailField = document.forms["register1"]["email"].value;
var atpos = EmailField.indexOf("#");
var dotpos = EmailField.lastIndexOf(".");
if (atpos < 1 || dotpos < atpos + 2 || dotpos + 2 >= EmailField.length) {
document.getElementById("emailmsg").innerHTML = " Invalid Email";
val = false;
}
if (EmailField == null || EmailField == "") {
document.getElementById("emailmsg").innerHTML = " Empty";
val = false;
}
//Main Login Validation Function -->
function validateLoginForm() {
resetMsg();
var val = true;
//Username Validation
if (isEmpty(log_in.username.value)) {
document.getElementById("usernamemsg").innerHTML = " Empty";
val = false;
}
//Password Validation
if (isEmpty(log_in.password.value)) {
document.getElementById("passwordmsg").innerHTML = " Empty";
val = false;
}
return val;
}
</script>
The validations won't work and I dont know why. This is a school project.
my main problem is that the script isnt running when im submiting the form ,when there even some errors at the form(what the user submits) it still goes to the next page and no innerHtml massage is shown.

Here, I went through your code, refractored a lot of it, wrote out some comments on how to improve it.
What stops the form from submitting is returning false. You're returning a variable called val, and if there is an error that variable is set to false, thus returning false and preventing the form from submitting.
I recommend taking the JS and putting it in your text editor and reading through everything. You should learn a good bit.
Here it is: http://jsfiddle.net/2x5LU/
I just did first name cause I have to work now, but you should be able to work off of this.
function validateForm(){
resetMsg();
var val = true;
if(isEmpty(firstName.value)){
firstNameMsg = 'Empty';
val = false;
}else if(isNumeric(firstName.value)){
firstNameMsg = 'Letters Only';
val = false;
}else if(isShort(firstName.value)){
firstNameMsg = 'Too Short';
val = false;
}
return val;
}

Javascript stopping form from passing data

resolved my javascript issue. Sorry it was mainly my fault as i copied and pasted my code instead of rewriting it out again. Strange thing is that it doesn't seem to pass the variables from the form to the process page as i have echo'd the SQL statement back out. This form did work previously to the java script all i added in was Post Code: for each row and even after deleting the javascript it still doesn't work :S
Sorry deadline tomorrow and im panicing.
<script type="text/javascript">
function checkForm()
{
var username = document.getElementById('username').value;
if(username.length < 5)
{
alert("Username is to short");
return false;
}
else if (username.length<16)
{
alert("Username is to long");
return false;
}
var firstName = document.getElementById('firstName').value;
if(firstName.length <3)
{
alert("Forname is to short");
return false;
}
var lastName = document.getElementById('lastName').value;
if (lastName.length <3)
{
alert("Surname is to short");
return false;
}
var address = document.getElementById('address').value;
if (address.length <8)
{
alert("Address is to short");
return false;
}
var town = document.getElementById('town').value;
if (town.length <3)
{
alert ("Town is to short");
return false;
}
var postCode = document.getElementById('postCode').value;
if (postCode.length <6)
{
alert ("Invalid Post Code");
return false;
}
else if (postCode.length>8)
{
alert("Invalid Post Code");
return false;
}
var cardType = document.getElementById('cardType').value;
if (cardType.length <3)
{
alert ("Please enter a valid card type");
return false;
}
var password = document.getElementById('password').value;
if (password.length <6)
{
alert ("You password must be between 6-12 characters");
return false;
}
else if(password.length>12)
{
alert ("Your password must be between 6-12 characters");
return false;
}
else
{
return true;
}
}
function checkUsername()
{
var username = document.getElementById('username').value;
var element = document.getElementById('username1');
if(username.length < 5)
{
element.innerHTML = "Username is to short";
element.style.color = "red";
}
else if (username.length >16)
{
element.innerHTML = "Username is to long";
element.style.color = "red";
}
else
{
element.innerHTML = "Username";
element.style.color = "green";
}
}
function checkFname()
{
var firstName = document.getElementById('firstName').value;
var element = document.getElementById('firstname1');
if(firstName.length < 3)
{
element.innerHTML = "Forname is to short";
element.style.color = "red";
}
else
{
element.innerHTML = "Forname";
element.style.color = "green";
}
}
function checkLname()
{
var lastName = document.getElementById('lastName').value;
var element = document.getElementById('surname1');
if(lastName.length < 3)
{
element.innerHTML = "Surname is to short";
element.style.color = "red";
}
else
{
element.innerHTML = "Surname";
element.style.color = "green";
}
}
function checkAddress()
{
var address = document.getElementById('address').value;
var element = document.getElementById('address1');
if(address.length < 8)
{
element.innerHTML = "Address is to short";
element.style.color = "red";
}
else
{
element.innerHTML = "Address";
element.style.color = "green";
}
}
function checkTown()
{
var town = document.getElementById('town').value;
var element = document.getElementById('town1');
if(town.length < 3)
{
element.innerHTML = "Town is to short";
element.style.color = "red";
}
else
{
element.innerHTML = "Town";
element.style.color = "green";
}
}
function checkPostCode()
{
var postCode = document.getElementById('postCode').value;
var element = document.getElementById('postcode1');
if(postCode.length < 6)
{
element.innerHTML = "Post code is to short";
element.style.color = "red";
}
else if (postCode.length>8)
{
element.innerHTML = "Post Code To Long";
element.style.color = "red";
}
else
{
element.innerHTML = "Post Code";
element.style.color = "green";
}
}
function checkCard()
{
var cardType = document.getElementById('cardType').value;
var element = document.getElementById('card1');
if(cardType.length < 3)
{
element.innerHTML = "Card is to short";
element.style.color = "red";
}
else
{
element.innerHTML = "Card Type";
element.style.color = "green";
}
}
function checkPassword()
{
var password = document.getElementById('password').value;
var element = document.getElementById('password1');
if(password.length < 6)
{
element.innerHTML = "Password is to short";
element.style.color = "red";
}
else if (password.length>16)
{
element.innerHTML = "Password is to long";
element.style.color = "red";
}
else
{
element.innerHTML = "Password";
element.style.color = "green";
}
}
</script>
<p><b><h3>Welcome User Please Register</h3></b></p>
<form action="registerUserProcess.php" id="registerUserForm" method="post" name="registerUserForm" >
<table>
<tr><td><label id="username1">Username:</label></td><td><input id="username" type="text" size="16" onBlur='checkUsername();'/></td></tr>
<tr><td><label id="firstname1">Forename:</label></td><td><input id="firstName" type="text" size="20" onBlur="checkFname();" /></td></tr>
<tr><td><label id="surname1">Surname:</label></td><td><input id="lastName" type="text" size="30" onBlur="checkLname();" /></td></tr>
<tr><td><label id="address1">Address:</label></td><td><input id="address" type="text" size="50" onBlur="checkAddress();" /></td></tr>
<tr><td></td><td><input id="address2" type="text" size="50" onBlur="" /></td></tr>
<tr><td><label id="town1">Town:</label></td><td><input id="town" type="text" size="50" onBlur="checkTown();" /></td></tr>
<tr><td><label id="postcode1">Post Code:</label></td><td> <input type="text" id="postCode" size="8" onBlur="checkPostCode();" /></td></tr>
<tr><td><label id="contact1">Contact No:</label></td><td> <input type="number" id="contact" size="12" onBlur="checkContactNo();" /></td></tr>
<tr><td>Card Number:</td><td><input type="number" id="cardNo1" size="4" /> - <input type="number" id="cardNo2" size="4" /> - <input type="number" id="cardNo3" size="4" /> - <input type="number" id="cardNo4" size="4" /></td></tr>
<tr><td><label id="card1">Card Type</label></td><td> <input type="text" id="cardType" size="8" onBlur="checkCard();" /></td></tr>
<tr><td>Email Address:</td><td><input id="emailAddress" type="text" size="50" /></td></tr>
<tr><td><label id="password1">Password:</label></td><td><input id="password" type="password" size="16" onBlur="checkPassword();" /></td></tr>
<tr><td><label id="terms1">Accept Terms & Conditions:</label></td><td><input type="checkbox" id="termsConditions" value="yes" onBlur="checkTerms();" /></td></tr>
<tr><td><input type="reset" id="resetForm" value="Reset" id="resetForm" /></td><td><input type="submit" id="submitUser" value="Submit" id="submitUser" onSubmit='return checkForm();' /></td></tr>
</table>
</form>

As others said, check your syntax. In checkform(), it should be
else if (username.length > 16)) instead of < 16
and in checkUsername() you spelled length wrong.
But your main problem is in your returns. In checkform() you should only put return true at the end when everything has been validated, or else the function just exit after the first validation.
You could also refactor all of this. You've got plenty of function that do almost the same thing. If you make one function that take minimum characters, maximum characters and the control to validate in parameters, you could do all of your code in 20 to 30 lines.
Plus, it seems like you copy-pasted some of your functions without changing the name of the variables or the targeted control. In fact, you assign Username as a variable in every function, but change the name in the condition, meaning you use an unassign variable.

Function: checkForm():
You need to change the second else if to:
else if (username.length<16)) needs to be > 16.
--
Function: checkUsername():
You have incorrectly spelled length. Change it to:
else if (username.length>16)

This is too much code for one question, but I noticed a few things in the first function:
else if (username.length<16) // This should probably be username.length > 16
{
alert("Username is to long");
return false;
}
if (isNAN(contact)) // this should probably be !isNaN(contact)
{
return true;
}

You misspelled length in the following: username.lenght>16
This is the reason your too long isn't working.
function checkUsername()
{
var username = document.getElementById('username').value;
var element = document.getElementById('username1');
if(username.length < 5)
{
element.innerHTML = "Username is to short";
element.style.color = "red";
}
else if (username.lenght>16)
{
element.innerHTML = "Username is to long";
element.style.color = "red";
}
else
{
element.style.color = "green";
}
}