Hey glannis,
Why would you want the same hit counter on every page? You should only have it seen on a splash page, start page or landing page...of your web site...then from there the user clicks onto a link that takes them to your "main" index of the oxwall script and your hit counter should never be seen again. Only when someone goes to your domain name index page is where you should have your counter.
Now say you don't want to have a splash page, start page or landing page...then this will be a custom code mod to the oxwall script. Remember every time you do an update you will have to replace your custom code again as it will be lost on the update.
I would place your hit counter code in the
/ow_system_plugins/base/views/components/sign_in.html file.
Check out how to customize this page by going to the link below, it has a lot of good stuff on how to change things in the Oxwall script.
Link: http://www.ewtnet.com/2013/06/how-to-create-custom-sign-in-page-in.html
hope this helps,
Wilson