How to create a visit counter ...

[NordComputer]

I think the easiest way would be to get a Google Analytics account and let Google track your visitors. You will have a lot more information than a simple counter and a better interface than whatever you could do by yourself.
You will just need to:
1. add your site to the Analytics Account
2. insert a simple Javascript code on every page that you want tracked.
The current layout of your website will not be changed. Google Analytics does not introduce any icons, images or links into your pages.