position:relative;z-index:10000px;
would definitely work, but it might interfere with your current layout. A better option could be:
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
function displayPopup (number) {
var context;
var dx= 4;
var dy=4;
var y=25;
var elWidth =150;
var ballWidth=10;
var x=(elWidth+ballWidth)/2;
var counter = 0;
var myCanvas=document.getElementById('myCanvas'+number);
function draw(){
context= myCanvas.getContext('2d');
context.clearRect(0,0,200,235);
context.beginPath();
context.fillStyle="red";
context.arc(x,y,10,0,Math.PI*2,true);
context.closePath();
context.fill();
if(y>200){clearInterval(interval);}
if( y<0 || y>200)dy=0;
y+=dy;
myCanvas.className='active';
}
var interval=setInterval(draw,10);
}
</script>
<style>
html,body{margin:0;}
div.time {
display: table;
background: green;
float: left;
margin: 20px;
zoom: 1;
position: relative;
top: 75px;
left:35px;
width: 150px;
height: 150px;
}
span {
display: table-cell;
text-align: center;
vertical-align: middle;
color: white
-webkit-touch-callout: none;
-webkit-user-select: none;
-khtml-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;
}
canvas{
z-index:10000;
transform: inherit;
float: left;
margin: 20px;
zoom: 1;
position: relative;
top: -200px;
left:35px;
margin:20px;
}
#myCanvas1{clear:left;}
</style>
</head>
<body>
<div class="time"><span>Past Thoughts</span></div>
<div class="time"><span>Present Thoughts</span></div>
<div class="time"><span>Future Thoughts</span></div>
<canvas id="myCanvas1" width="150" height="235" onclick="displayPopup(1)"></canvas>
<canvas id="myCanvas2" width="150" height="235" onclick="displayPopup(2)"></canvas>
<canvas id="myCanvas3" width="150" height="235" onclick="displayPopup(3)"></canvas>
</body>
</html>
http://fiddle.jshell.net/uvrkgrqs/show/