Have a custom plugin do something on every page load?
Add a init() method to your plugin and as long as it's installed and enabled, it'll be called on every request.

public function init()
{
    parent::init();

    /* Do your stuff */
}


If you want it to only happen on front-end requests, you can use:

if (craft()-&gt;request-&gt;isSiteRequest()) { ... }