As a web developed CSS is very important and often one of the first elements you will learn about. CSS helps to design the page, setting sizes, positions, fonts and colour of different elements you have on your page. Not all browsers support the same CSS functions so it is important that you keep up to date on what works on what browsers to make sure that you site performs well on all of them not just one of two. CSS is all about boxes. Everything that is displayed on the screen has a box. Each element is given a width but then you can also add padding and borders to this meaning that the placeholder needed for that box will take up more room than the actual width of the element. With people using a number of different screen sizes to view websites it is important that you make your design responsive so that elements shrink and enlarge to fit the screen they are being viewed on. If you do not do this, not only will your website not display properly to some people but you may also get penalised by the likes of Google in the search engine results pages and find that you get pushed further down.