Creating a website using div elements and CSS for structure is the norm -- it offers a more lightweight solution than tables by using significantly less code. This reduces the size of your pages ...

How to Override CSS Inside DIV Classes. If you ever need to tweak the appearance of a page on your business website, you may have to modify Cascading Style Sheet code.

Tony Patton focuses on CSS fundamentals and explains how multiple rules for the same element are handled. Multiple rules ensure that there will be no surprises for either you or the user community.

AFAIK, CSS cannot affect the DOM tree. So, display: none just says the element should not be displayed, not that it should cease to exist. Style/structure separation and all that.