Let's say that you've done a nice layer. The site you've designed your layout for has say 20 pages. Then suddenly the client tells you to 'forget about the header'. Will you have to open and edit the 20 pages to remove that 'no longer wanted header'? Or what would you do if, suddenly, your client wanted to add a recursive element under the page header? Would you add it on the 20 pages?
My guess, in order to avoid that problem, was to include (server-side) the generic parts of the layout (the ones that will be used on every page of the site). That way, I would have to remove one element once and this mod in the included file would therefore affect all the generic pages.
Is there another way to do it? How do you css people deal with it? Thanks in advance for your help and your answers.