ID vs CLASS in CSS. Please explain in detail with example

Question

I have heard that ID is unique and can only be used once in a page, but its working fine when used over multiple times on a page. Please let me know the purpose of ID and hows i

Answer 1

If I can use an analogy of cars:

ID is like a Registration Plate

• supposed to be unique - allows you to uniquely identify and style a single element

Class is like a Vehicle Model

• allows you to deal with a set of related elements in one go.

Continuing the anaology:

It's fine to duplicate registration plates in so far as the cars still work - but the police would get quite annoyed! How would you identify a particular driver as having been speeding?

The same applies with HTML elements - reusing the same ID just stops you identifying a single element when you need to.