Every time that WordPress comes out with a new version, you see the familiar yellow bar at the top that tells you there’s a new version out. It’s convenient for upgrading but inconvenient if you aren’t sure what version of WordPress you’re currently running. When there is no upgrade available, you can always look at the lower right corner and it’ll tell you which version. When there’s an upgrade, that helpful text is replaced with a link to upgrade.
So if you need to upgrade, what’s the easiest way to find out your current version? If you are logged in then it’s quite easy. Find the WordPress logo in the upper left, click it and then select “About WordPress.” That’ll load up the About page, which has the version number clearly at the top.
If you’re not logged in, you can often look at the source and see a meta generator tag that says what version it is. It’ll look like this:
< meta name="generator" content="WordPress 3.5.1" />
But many site owners remove it because it can be a liability, bots can scan the interwebs for old versions that are easily hacked (there are still ways to scan but why make it so easy?), so people usually remove it. If you want to remove that tag, you can add this to your theme’s functions.php file:
Hope that helps!