Ability to disable javascripts , disable client-side features.

Edit Subject

let the user the ability to disable java scripts on the run, for example some flying boxes offering you to sign up each time you visit. because other people might want them to be featured it and it doesnt track you anymore than the site itself, the average user should decide if he want the feature off for himself only.

I was on this site that had this giant object of a twitter bird flying on the webpage disturbing my reading act, i imidiatly wanted to disable it, the fact that it is showed all over the website is bad.

ofc any more than the average user can just make a userscript to disable it but what about the non technical people?