For some reason, some JavaScript implementations mix up HTML element IDs and code. If you use a different ID for your submit button it will work (id="somethingelse" instead of id="submit"):

<input type="button" value="Sign Up" class="signupinput" onClick="verifypass()" id="somethingelse" />

(I think id="submit" has the effect that the submit method is overwritten on the form node, using the button node. I never figured out why, perhaps to allow shortcuts like form.buttonid.value etc. I just avoid using possible method names as IDs.)

I think it would be better if you do it real time, for send error when the user leave each input. For example, there is an input, where you set the email address. When the onfocusout event occured in Javascript you can add an eventlistener which is call a checker function to the email input. There is a quick example for handling form inputs. (Code below) It is not protect you against the serious attacks, because in a perfect system you have to check on the both side.

Description for the Javascript example:

• There is two input email, and password and there is a hidden button which is shown if everything is correct.
• The email check and the password check functions are checking the input field values and if it isn't 3 mark length then show error for user.
• The showIt funciton get a boolean if it is true it show the button to submit.
• The last function is iterate through the fields object where we store the input fields status, and if there is a false it return false else its true. This is the boolean what the showIt function get.

Hope it is understandable.

<style>
#send {
  display: none;
}
</style>
<form>
<input type="text" id="email"/>
<input type="password" id="password"/>
<button id="send" type="submit">Send</button>
</form>
<div id="error"></div>

<script>
var fields = {
    email: false,
  password: false
};

var email = document.getElementById("email");
email.addEventListener("focusout", emailCheck, false);
var password = document.getElementById("password");
password.addEventListener("focusout", passwordCheck, false);

function emailCheck(){
    if(email.value.length < 3) {
    document.getElementById("error").innerHTML = "Bad Email";
    fields.email = false;
  } else {
    fields.email = true;
    document.getElementById("error").innerHTML = "";
  }
  show = checkFields();
  console.log("asdasd"+show);
  showIt(show);
}

function passwordCheck(){
    if(password.value.length < 3) {
    document.getElementById("error").innerHTML = "Bad Password";
    fields.password = false;
  } else {
    fields.password = true;
    document.getElementById("error").innerHTML = "";
  }
  show = checkFields();
  console.log(show);
  showIt(show);
}

function showIt(show) {
    if (show) {
    document.getElementById("send").style.display = "block";
  } else {
    document.getElementById("send").style.display = "none";
  }
}


function checkFields(){
    isFalse = Object.keys(fields).map(function(objectKey, index) {
    if (fields[objectKey] === false) {
        return false;
    }
    });
  console.log(isFalse);
  if (isFalse.indexOf(false) >= 0) {
    return false;
  }
  return true;
}
</script>

I'm not sure why that's not working, but you get around having to call form.submit(); if you use a <input type="submit"/> instead of <input type="button"/> and then use the onsubmit event instead of onclick. That way, IIRC, all you have to do is return true or false.