Here's how you reference the normal BNF:Joint Formulary Committee (2007). British National Formulary. 54th edition. London: British Medical Association and Royal Pharmaceutical Society of Great...
CSS is Cascading Style Sheets. Basically CSS allows a web developer/designer to quickly change and alter the look and feel of an entire website. This is a huge step up from having to create inline...
Just reference it like you would a page in a book. Here is a resource to help you with Harvard referencing. http://www.neilstoolbox.com/bibliography-creator/index.htm