[support] CSS Links in generated HTML

[Martin Hooper]

Looking at my generated source code for pages what are the ?5 at the
end of each stylesheet link?

<link type="text/css" rel="stylesheet" media="all"
href="/drupal/modules/node/node.css?5" />
<link type="text/css" rel="stylesheet" media="all"
href="/drupal/modules/system/defaults.css?5" />

I'm just curious thats all as I have never seen a decleration of a
stylesheet like that before!