Neocities.org

guys im sorry im a coding newbie how do i make a page change on a button's click?? i want the link before clicked to be something like "/stairs", then, when the button is clicked, i want the div present to change to another and the link to change to something like '/stairs/case'! like, all in the same html file, if possible?? if not, how do i make another html file with two slashes? (´･ω･`)