Question

Duplicate:

• Cascading style sheets use “id” or “class”
• CSS: are class and id interchangeable?
• div class vs id
• CSS: div id VS. div class

Sometime, when I like to make a selection a add an ID (unique) to something (images) and i used jquery to do domething when hover or click.

But the same thing can be done with classes. I understand that class is for a lot of thing (let’s say class="selected") but when a class is added to something, I can trigger a jQuery action with that class insted of ID…

So the question is, what is "the right way" to use class and ID if I can accomplish anything and everything with both !

Answer 1

Where to use an ID versus a class

The simple difference between the two is that while a class can be used repeatedly on a page, an ID must only be used once per page. Therefore, it is appropriate to use an ID on the div element that is marking up the main content on the page, as there will only be one main content section. In contrast, you must use a class to set up alternating row colors on a table, as they are by definition going to be used more than once.

IDs are an incredibly powerful tool. An element with an ID can be the target of a piece of JavaScript that manipulates the element or its contents in some way. The ID attribute can be used as the target of an internal link, replacing anchor tags with name attributes. Finally, if you make your IDs clear and logical, they can serve as a sort of “self documentation” within the document. For example, you do not necessarily need to add a comment before a block stating that a block of code will contain the main content if the opening tag of the block has an ID of, say, ‘main’, ‘header’, ‘footer’, etc.