JavaScript - Default Event Not Stopping Even With Return False;

<script type="text/javascript">

function changeColor(color) {
document.getElementById("nav").style.borderColor = color;
}

</script>

<a href="index.php" onclick="changeColor('red') ;return false">HOME</a>
<a href="about.php" onclick="changeColor('blue') ;return false">ABOUT</a>
<a href="contact.php" onclick="changeColor('orange') ;return false">CONTACT</a>

function updateStockRequest(thestatus,theform,thedate) {

	if(thestatus == 'locked') {
		if(checkStockRequested()) {
			if(confirm('Are you sure you want to send for processing?\nYou will not be able to add any more stock!')) {
				document.getElementById('status').value = 'locked';
				document.forms[0].submit();
			}
		} else {
			alert('You must request some stock first!');
		}
	}
}

function checkStockRequested() { //check to see if stockrequest has items added!!!

	xmlHttp=GetXmlHttpObject()
	if (xmlHttp==null) {
		alert ("Browser does not support HTTP Request");
		return;
	}

	var params = "?theuid=" + escape(document.getElementById('uid').value);
	var url="_check_stockrequest.php"
	url=url+params;
	ajaxedInner = "";
	xmlHttp.open("GET",url,true);
	xmlHttp.setRequestHeader("If-Modified-Since", "Fri, 31 Dec 1999 23:59:59 GMT");
	xmlHttp.onreadystatechange=stateChanged;
	xmlHttp.send(null);
	xmlHttp.onreadystatechange = function() {
		if (xmlHttp.readyState == 4){
			if (xmlHttp.status == 200) {
				responsestring = xmlHttp.responseText.replace(/^\s+|\s+$/g, '');
				alert(responsestring);
				if(responsestring == 'true') {
					return true;
				} else {
					return false;
				}
			}
		}
	}
}

<SCRIPT type="text/javascript">
	function validateForm() {
		if (document.forms["form"]["quantity"].value== (+$row['quantity']) {
			alert ("Cannot submit because the quantity specified is not available.");
			return false;
		}
	}
</SCRIPT>
<INPUT name="quantity" onsubmit="return validateForm()>

<asp:button runat="server" id="btnChangeCommentsAuth" CSSclass="RaiseButton" OnClientClick="CommentsCheck('MainDisplayContentChange_txtAuthCommentsArea');" PostBackUrl="~/RaiseTaskChange.aspx" Text="Auth" />

function CommentsCheck(comments) 
{
    var com;
    var result = new boolean();
    com = document.getElementById(comments);
    if (document.getElementById(comments).value == '') {
        com.style.backgroundColor = "#B20635";
        result = 0;
    }
    else 
    {
    result = 1
    }
}

      <script type="text/javascript">
    //FIRST FUNCTION FOR FORMS[0]
    function signinForm(){
    
    		// var sameWarning = "The required fields were not submitted for the following error(s).  \n \n";
    		var warningLogin = "The following field(s) require an entry: \n \n";
    		var sameWarning = warningLogin;
    		
    		var userName = document.forms[0].userName.value;
    		var pswd = document.forms[0].pswd.value;
    		
    		if(userName == ""){ 
    		sameWarning += " - First Name \n";
    		}
    		
    		if(pswd == ""){ 
    		sameWarning += " - Password \n";
    		}
    
    		if (warningLogin == sameWarning){ 
    			return true; 
    			}
    		
    		else  { 
    			window.alert(sameWarning); 	
    		}
        return false;	
       }
     
  //SECOND FUNCTION CALL FOR FORMS[1] 
    function saveSignUp(){
    
    		// var warning = "The required fields were not submitted for the following error(s).  \n \n";
    		var warning = "The following field(s) require an entry: \n \n";
    		var same = warning;
    		
    		var firstName = document.forms[1].firstName.value;
    		var lastName = document.forms[1].lastName.value;
    		var email = document.forms[1].email.value;
    		var phone = document.forms[1].phoneNumber.value;
    		
    		if(firstName == ""){ 
    		//firstName.style.backgroundColor="red";
    		warning += " - First Name \n";
    		}
    		
    		if(lastName == ""){ 
    		warning += " - Last Name \n";
    		}
    
    		if(email == ""){ 
    		warning += " - Email \n";
    		}
    
    		if(phone == ""){ 
    		warning += " - Work Phone \n";
    		}
    		
    		if(phone < 5 ){
    			warning += " - Must be a numberssss \n";
    			}
    
    		if (warning == same){
    			return true; 
    		} 
    		
    		else  { 
    			alert(warning); 		
    		}
    	return false;
       }
       
    </script>

    <h1>Login</h1>
    <form method="post" onsubmit="return signinForm();" action="" >
        <input type="text" placeholder="Username/Email" name="userName">
        <input type="password" placeholder="Password" name="pswd" id="pswd">
        <input type="submit" onclick="signinForm();" value="Sign In">
    </form>
    <h1>Sign Up!</h1>
        <form method="post" onsubmit="return saveSignUp()" action="" >
        <input type="text" placeholder="First Name" name="firstName">
        <input type="text" placeholder="Last Name" name="lastName">
        <input type="text" placeholder="Email" name="email">
        <input type="text" placeholder="Phone Number" name="phoneNumber">
        <input type="submit" onclick="saveSignUp();" class="button wide" value="Request an Account">		
</form>

function chapter12_nodeOne() {
    
    //create an element
    var element = document.createElement('input');
    //set some attributes
    element.setAttribute('type', 'button');
    element.setAttribute('value', 'submit');
    element.setAttribute('id', 'myBtn');
    //appendd the element into a DIV
    document.getElementById('myDiv').appendChild(element);
    //uses EventUtil to attach an event listener
    EventUtil.addHandler(element, 'click', function() {
        alert('event attached');
    });

    var flag = confirm('prevent default behavior of button?');
    if (flag) {
        var el = document.getElementById('myBtn');/////////////////////////(1)
        var ev = el.onclick;
    }
}

var EventUtil = {
    addHandler: function(element, type, handler) {
        //check if the element and the browser support DOM Level 2 event attachment
        //if the user is not browsing with IE
        if (element.addEventListener) {
            element.addEventListener(type, handler, false);
        }
        //if user is browsing with IE
        else if (element.attachEvent) {
            element.attachEvent("on" + type, handler);
        }
        //if user is using a browser that only supports DOM Level 0 event attachment 
        else {
            element["on" + type] = handler;
        }
    },

    removeHandler: function(element, type, handler) {
        //check if the element and the browser support DOM Level 2 event attachment
        //if the user is not browsing with IE
        if (element.removeEventListener) {
            element.removeEventListener(type, handler, false);
        }
        //if user is browsing with IE
        else if (element.detachEvent) {
            element.detachEvent("on" + type, handler);
        }
        //if user is using a browser that only supports DOM Level 0 event attachment 
        else {
            element["on" + type] = null;
        }
    }
};

// Values for fading
var fadeBy = 10; //Amount to fade by
var fadeTime = 120; //Time in milliseconds to fade. 
var ie_counter = 0; //Counter for crappy IE.
var fade_to = 70;
function fader(obj) {
    var div = document.getElementById(obj);
	
    //Object details
    var opacity = div.style.opacity * 100 + fadeBy; //Fade (FF)
    ie_counter = ie_counter + fadeBy;
    var opacity_ie = div.style.filter = "alpha(opacity=" + ie_counter + ")"; //Fade (IE)
    div.style.opacity = opacity / 100;
	if ( ie_counter != fade_to || opacity != fade_to ) {
    	setTimeout( "fader('" + obj + "')", fadeTime );
	}
}

$(document).ready(function(){
	
	var Cycle = setInterval('cycle()', 3000);
	
	/* ... some other functions here ... */
   
	$('.Test').click(function(){
		var ID = $(this).attr('ID');
		clearInterval(Cycle);
                /* ... Rest of this function ... */
                if (ID == 'Home')
		{
			var Cycle = setInterval('cycle()', 3000);
		}
		console.log(ID);
        });
});