Once again I have to give firefox credit for giving users the tools in about:config to disable this. It's cute fluff at best and annoying/abusive at worst.
The browser's UI should more or less be fully off the table when it comes to what a website can change, and that includes scrollbars.
The browser's UI should more or less be fully off the table when it comes to what a website can change, and that includes scrollbars.