Grid centering

How do I center the grid within the browser window?

Just use HTML centering. <center> ... </center>

where would I put the HTML statement? (sorry but I'm very new to this)

You would place it around the section of JavaScript code you use to create your grid. E.g. -
<center>
<script>
AW code here
</script>
</center>
An alternate method would be to create a div with CSS definitions to center its contents and place the AW grid within that. This is a little more complicated that the above (by only slightly so).

This did not work any ideas why? Does the AW grid not have a centering command?

No, it doesn't. You may need to post an example of your code or put it up on the web.