Want HTML form submit to do nothing

By using return false; in the JavaScript code that you call from the submit button, you can stop the form from submitting.

Basically, you need the following HTML:

<form onsubmit="myFunction(); return false;">
    <input type="submit" value="Submit">
</form>

Then the supporting JavaScript code:

<script language="javascript"><!--
    function myFunction() {
        // Do stuff
    }
//--></script>

If you desire, you can also have certain conditions allow the script to submit the form:

<form onSubmit="return myFunction();">
    <input type="submit" value="Submit">
</form>

Paired with:

<script language="JavaScript"><!--
    function myFunction() {
        // Do stuff
        if (condition)
            return true;

        return false;
    }
//--></script>