Comments on: class vs. ID

By: LawLawLaw: Erik J. Heels

LawLawLaw: Erik J. Heels — Wed, 30 Nov -0001 00:00:00 +0000

Movable Type Brain Dump
Tips and tricks I wish I had known when I started using Movable Type.

By: Just Orb

Just Orb — Wed, 30 Nov -0001 00:00:00 +0000

Simple explanation.
Thanks to Scriptygoddess, I now understand the difference between the CSS tags "div id" and "div class". My CSS is

By: ste

ste — Wed, 30 Nov -0001 00:00:00 +0000

Yeah, from what I've read, the main differences between ID and class are that ID is applied only the first time it is used in a document where class can be applied to many different instances. So for example, you could have defined:
#pageHead { properties },
and in your document, only the first

would have the properties specified. And contrasting, you could have defined:
.sectionHead { properties },
and any

in your document would have the properties. For most uses, I think it's better to use classes, unless you're absolutely certain you're only going to use the ID once (or want to make sure you only use the ID once).

By: kristine

kristine — Wed, 30 Nov -0001 00:00:00 +0000

Also – when I just set up my newest skin, I used ID's to absolutely position the background images. I figured that I would never use #top1 – #top6 accidently as classnames, and since there was only one of each image, I'd insure that they were the only things that got absolutely positioned the way they did I notice that Image Ready does this if you tell it to generate CSS instead of Tables, too.

By: kristine

kristine — Wed, 30 Nov -0001 00:00:00 +0000

Here's my example of ID vs Class – In the MT default templates, there's a #content and a #links. These are the 2 main sections of the page (main posts and sidebar), and because they are only referred to once in the html, they are IDs instead of classes.
Personal thought – I think this is a stronger definition than a class definition, when you look at the cascading of the stylesheet. It seems to be more important, and that works well if you are only going to have that section once in the document.

Ahh, and Here's more info on this subject – I knew I'd read more somewhere! This explains what I said a bit better

By: Jennifer

Jennifer — Wed, 30 Nov -0001 00:00:00 +0000

Can anyone give me a "good" example of when to use IDs over classes? (If there is one?? Or as a general rule should one just use class= all the time and forget the whole ID thing?)

(And Erica brought up another question… when do you use # or . when defining a custom class? – I always use . but you can # and still call it with class="classname".)

By: Shawn

Shawn — Wed, 30 Nov -0001 00:00:00 +0000

This is actually just a side effect. The real reason for the two is that Microsoft defined ID (and uses it when writing Microsoft-specific COM objects to interface with a web page), while the W3C defined the class attribute with a similar function.

By: Cis

Cis — Wed, 30 Nov -0001 00:00:00 +0000

For pratical purposes though, using the same ID division more than once in a single page can cause problems with your site resolving properly. The best HTML comparison would be the NAME attribute, I think.

By: erica

erica — Wed, 30 Nov -0001 00:00:00 +0000

Ah I don't blame you, I had to look into it a few months ago, and I still always end up using # instead of . or vice versa.

By: erica

erica — Wed, 30 Nov -0001 00:00:00 +0000

What my understanding was;
"The difference is an ID is unique to one area, classes are not. Thus IDs can be used in conjunction with Javascript/DHTML."