You need to implement this CSS in all the documents loaded. You can do this modifying the DOM for the document you load. If you are to provide static content, I would recommend putting the CSS into the content instead, as that is easier to modify later.
Here's a small example on how to style the scrollbars:
::-webkit-scrollbar { width: 42px; } ::-webkit-scrollbar-track-piece { background: #CCCCCC; border: 2px solid #6666CC; -webkit-border-radius: 10px; width:20px; } ::-webkit-scrollbar-thumb:vertical { height: 40px; border: 2px solid #6666CC; background-color: #6666CC; -webkit-border-radius: 10px; } ::-webkit-scrollbar-button:end:increment { height:42px; width:42px; background-image: url(arrow-down.png); background-repeat:no-repeat; background-color:white; } ::-webkit-scrollbar-button:start:decrement { height:42px; width:42px; background-image: url(arrow-up.png); background-repeat:no-repeat; background-color:white; } ::-webkit-scrollbar-button:end:increment:hover { background-color:green; } ::-webkit-scrollbar-button:start:decrement:hover { background-color:green; } :not(.none):not(.double-start)::-webkit-scrollbar-track-piece:vertical:end:single-button, :not(.none):not(.double-start)::-webkit-scrollbar-track-piece:vertical:end:double-button, .single::-webkit-scrollbar-track-piece:vertical:end, .double-end::-webkit-scrollbar-track-piece:vertical:end, .double-both::-webkit-scrollbar-track-piece:vertical:end { margin-bottom: 40px; } :not(.none):not(.double-end)::-webkit-scrollbar-track-piece:vertical:start:single-button, :not(.none):not(.double-end)::-webkit-scrollbar-track-piece:vertical:start:double-button, .single::-webkit-scrollbar-track-piece:vertical:start, .double-start::-webkit-scrollbar-track-piece:vertical:start, .double-both::-webkit-scrollbar-track-piece:vertical:start { margin-top: 40px; }
This is just an example, and you probably want to change it a lot to suite your needs.