RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
newbie questions... What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID. ¤ devendra ¤ In addition to everything else, as id replaces name, id becomes a means to navigate to parts of a document using the anchor element: a id=main/a. drew ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
Re: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
On Thu, 10 Feb 2005 06:40:49 -0500, Trusz, Andrew [EMAIL PROTECTED] wrote: newbie questions... What is the advantage of the fact that IDs must be unique on a page? 1. getElementById() works. 2. Validation. If you use div id=maincontent, validator will complain when you have two or more such divs (typical copypaste accident :) Additionally IDs have higher priority than class in CSS, so it's easier to make local styles for element with an ID than with a class. -- regards, Kornel Lesiski ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
You can address elements from the DOM (Document Object Model) directly via JavaScript. Cheers, Mike Pepper Accessible Web Developer Internet SEO and Marketing Analyst [EMAIL PROTECTED] http://www.visidigm.com Administrator Guild of Accessible Web Designers [EMAIL PROTECTED] http://www.gawds.org -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Trusz, Andrew Sent: 10 February 2005 11:41 To: 'wsg@webstandardsgroup.org' Subject: RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes? newbie questions... What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID. ¤ devendra ¤ In addition to everything else, as id replaces name, id becomes a means to navigate to parts of a document using the anchor element: a id=main/a. drew ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help ** -- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.300 / Virus Database: 265.8.6 - Release Date: 07/02/05 ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
-Original Message- From: [EMAIL PROTECTED] On Behalf Of Kornel Lesinski Sent: Thursday, February 10, 2005 7:09 AM To: wsg@webstandardsgroup.org Subject: Re: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes? newbie questions... What is the advantage of the fact that IDs must be unique on a page? 1. getElementById() works. 2. Validation. If you use div id=maincontent, validator will complain when you have two or more such divs (typical copypaste accident :) Additionally IDs have higher priority than class in CSS, so it's easier to make local styles for element with an ID than with a class. -- regards, Kornel Lesiski * While true all those points had already been mentioned and weren't the point in any case. The point was that you can create links to parts of documents using id: www.mysite.com/mypage.html?id=#myidea drew ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
I thought I should pick up on the comment by Peter and ask one of my many newbie questions... What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID. Apologies if this question is not appropriate for this list and should be directed more to a CSS-specific list. ¤ devendra ¤ -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Asquith Sent: Wednesday, February 09, 2005 3:12 PM To: wsg@webstandardsgroup.org Subject: Re: [WSG] Not and IE bug?!? Hi Peter Peter Flaschner wrote: Well, the clearing didn't do it. At least not as I understand it. If you're following the lead of the page you mentioned, you will find removing the overflow: hidden; line from the style sheet should solve your problem. By setting the height to zero and then hiding the overflow you're effectively removing the clearer block from the page layout. Setting visibility to hidden, on the other hand, allows the block to take its specified position and size but not be rendered by the browser. I.e. it still takes up the space it would have. I note, too, that your example page contains multiple elements sharing the same ID. IDs must be unique for a given page. Cheers Peter -- Peter Asquith http://www.wasabicube.com/ ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help ** ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
The main advantage of using an ID is simply that it uniquely identifies the element. So your CSS or DOM scripting can target it alone. -- Iain Gardiner http://www.firelightning.com -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Devendra Shrikhande Sent: 09 February 2005 22:27 To: wsg@webstandardsgroup.org Subject: RE: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes? I thought I should pick up on the comment by Peter and ask one of my many newbie questions... What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID. Apologies if this question is not appropriate for this list and should be directed more to a CSS-specific list. ¤ devendra ¤ -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Peter Asquith Sent: Wednesday, February 09, 2005 3:12 PM To: wsg@webstandardsgroup.org Subject: Re: [WSG] Not and IE bug?!? Hi Peter Peter Flaschner wrote: Well, the clearing didn't do it. At least not as I understand it. If you're following the lead of the page you mentioned, you will find removing the overflow: hidden; line from the style sheet should solve your problem. By setting the height to zero and then hiding the overflow you're effectively removing the clearer block from the page layout. Setting visibility to hidden, on the other hand, allows the block to take its specified position and size but not be rendered by the browser. I.e. it still takes up the space it would have. I note, too, that your example page contains multiple elements sharing the same ID. IDs must be unique for a given page. Cheers Peter -- Peter Asquith http://www.wasabicube.com/ ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help ** ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help ** ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
Re: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
Hi Devendra
Devendra Shrikhande wrote:
What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID.
This is an important topic. At first glance, it would seem that there is
little need for an id attribute - why not use classes everywhere?
However, there's a semantic difference between ids and classes, which is
this: it's basically the difference between individuals and groups.
An id identifies a specific individual element of the document markup
and allows CSS to be written that addresses that element specifically.
In addition, you can reference the id in DOM (Document Object Model)
scripting to access an element using the getElementById() function.
A class, on the other hand can apply to many elements, not necessarily
of the same type - you could have a class called warning that is
applied to h1, p, li and so on to emphasize a warning condition,
for instance. Another example (which is pertinent to the thread that you
came in on) is where you want a class to clear floats. It may be that
you need to apply that class on more than one occasion in a particularly
fluid layout. By creating a clearer class you can apply it to any
appropriate block element in order to clear the preceding floats.
Another thing to bear in mind is that ids have higher precedence than
classes in determining what style is applied to a given element. This
means that
#myid {
color: blue;
}
.warning {
color: red;
}
will colour the element
p id=myid class=warningHello!/p
in blue (despite the fact that the .warning directive appears later in
the CSS cascade).
(To ensure that it's red you would need to add
#myid.warning {
color: red;
}
to your stylesheet).
If you carefully lay out your document, with ids for all the main
display blocks, you can set global class styles and then override them
on a block-by-block basis via the blocks' ids. So, for instance it might
be appropriate to display elements with the warning class differently
in a main content block as opposed a summary block.
Eric Meyer covers this topic well on pages 36-38 of his Cascading
Stylesheets The Definitive Guide 2nd Edition.
Having said all that, be wary of overusing ids and classes. By using CSS
selectors carefully, a lot of unnecessary classitis can be avoided.
Hope that helps
Peter
**
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See http://webstandardsgroup.org/mail/guidelines.cfm
for some hints on posting to the list getting help
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Re: [WSG] Not and IE bug?...follow up difference why a difference between IDs and classes?
I thought I should pick up on the comment by Peter and ask one of my many newbie questions... What is the advantage of the fact that IDs must be unique on a page? I am aware of the circumstance that if you need to repeat an ID, set is as a class, but have still not figured out the advantage of an ID. If you used absolute positioning, or a background image of the company branding, or a structure only appropriate for the main navigation, or some other set of styles that should only be rendered if they are unique on the, then it is useful to have IDs instead of classes. In today's browsers, put multiple IDs on a page and the page is ok, if maybe unusually styled. But future browsers are likely to be more strict and may display a big fat parse error message for such a page. That's a good thing -- it'll help you identify when you accidentally gave two id=nav styles to teh same page. It will be problematic, however, when you combine templates, CMSs, and webservices-sourced XML all in one document. This is where we are rescued by namespaces and the increasingly common habit of giving IDs unique prefixes based on the author. -- Ben Curtis : webwright bivia : a personal web studio http://www.bivia.com v: (818) 507-6613 ** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list getting help **
