Writing about web page http://www2.warwick.ac.uk/fac/arts/theatre_s/cp/study/design/resources/robertstechnical/session3/part1/
a content refers to appearance whereas presentation indicates that visual look and layout of the page. e.g. if you want all titles of the page to appear in red colour(presentation), then you would have to add something to each of the titles that makes it red.(content)
advantages;you would be able to arrange more easily,(e.g. you dont have to worry about the possibility of changing position phicically when you wannna replace it.you can update the page or whole website quicker, you may use the language called CSS when you wanna define presentaion separately.