Reading Sitepoint’s HTML5:Basics . The discussion of the ‘structure’ of HTML 5 was giving me a hard time because I keep associating structure with CSS. But I am now thinking of ‘structure’ like laying out all the parts of a bicycle. That’s your document, each part is a piece or element of the over all structure and each is a structure as well. You may have an idea of how to put all those pieces together but someone else may come along and put them together differently or even change the size of some pieces but the structure of each piece stays the same. A wheel is still round, the handlebars are still the same shape. CSS is what changes the look, how the pieces, the structures, are arranged. HTML 5 is the structure of each piece and the overall structure of the document, such as what is the main piece, what structure is a footer. I could also think of each element of the document being like a house – a structure – and CSS is what arranges the houses into neighborhoods.