[Joe Develper]

Whats a difference between id and class? I am bit confused about it.

[Rob Kaper]

IDs are unique: no two elements can have the same ID (and no element can have more than one ID).

Classes can be reused: multiple elements can have the same class (and elements can have multiple classes at once).

[Joe Develper]

hmm Thanks for your help, Rob.I appreciate it.

[temhawk]

Also, you can use both an ID and a class (or multiple classes) on the same element, and the name of the ID can be the same as the class (or one of the classes).

The following is valid:

<div id="foo" class="foo bar">Lorem ipsum...</div>

(Note that "foo" and "bar" are two different classes, separated by a space.)

This post has been edited by temhawk: 10 December 2010 - 06:34 PM

[Rob Kaper]

Note that if you use Ajax classes become increasingly less important now that browsers have better and faster support for CSS attribute selectors.

Because IDs need to be unique* you'll often end up with IDs such as comment_1 to avoid a collision with user 1, article 1 etcetera. You can still select all comments with the selector [id=^comment_] which selects all elements where the id attribute starts with comment_, effectively removing the need to also have a comment class. On elements you won't need to select uniquely classes are still preferred for performance.

[Joe Develper]

I appreciate your help guys to understand this concept. Thanks once again.

[denny]

Thanks for clarifying between ID and Classes.I was bit confuse.

[che09]

ID's are unique

* Each element can have only one ID
* Each page can have only one element with that ID
ID's have special browser functionality
Here is one: your code will not pass validation if you use the same ID on more than one element. Validation should be important to all of us, so that alone is a big one.

Classes are NOT unique

Any styling information that needs to be applied to multiple objects on a page should be done with a class.


Both, Classes and ID's don't have any styling information to them all by themselves. They require CSS to target them and apply styling.

[JakeMcGreg]

Now I understand it better. Reading about ID stuff gives me more info. Thanks for elaborating on that one.

[EncoderDecoder]

Quote

The key thing to know is that IDs identify a specific element and therefore must be unique on the page – you can only use a specific ID once per document. Many browsers do not enforce this rule but it is a basic rule of HTML/XHTML and should be observed. Classes mark elements as members of a group and can be used multiple times, so if you want to define a style which will be applied to multiple elements you should use a class instead.

- found this over the net..