.i opened it from the notepad.
its just 1 specific page. .and i wanted to change the html of the site after i used stylish for the css .
maybe i sound stupid but i want to know is it possible ( like the css parts )
That only changes the CSS for the current view of the page so you can check the effect of the change. You need to actually update the source file itself with the same change in order for it to be seen by everyone.
Similarly if you view the page source in notepad and make changes there you need to upload the changed file back to the site if you want the changes to show up.