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IDs are great because they allow you to give a unique ID to every element in the DOM, if you wish.

The most obvious reason is CSS selectors; you know exactly which elements will be affected beacuse there's only one per page

Where IDs really come in handy is DOM manipulation. - [old fashion] javascript uses the function getElementById() to interrogate the DOM.

Although new javascript libraries (such as jquery) allow you to use Xpath selectors to get DOM elements; getElementById is still the base root of the idea.

So now you're asking "why would i want to use javascript to interrogate the DOM?"

That's a pretty easy answer too - when working with a lot of content, custom animations, server applications, XML and / or AJAX it becomes a necessity to have some computer-based intelligence about the static HTML.

HTML doesn't do anything apart from structure the page; and if you want to play with that structure you need to have some client side (javascript) software that bridges the gap between user and plain text HTML

Here's an example of some DOM manipulation: http://xeneco.co.uk/extjs

DOM - Document Object Model

it's the node tree of any given webpage; ie how the elements are nested, etc

nodes can have attributes, with values, and content.

eg

<div id='menu'>

 <ul>

  <li><a href='#'>link</a></li>

  <li><a href='#'>link</a></li>

  <li><a href='#'>link</a></li>

  <li><a href='#'>link</a></li>

 </ul>

</div>

the div has an id attribute with the value 'menu'

[Xpath DOM example]

a link can be indentified by #menu/ul/li/a (this selects the node)

#menu/ul/li/a/@href gives the value of the link, etc etc

The DOM is how a computer sees a web page, and you can play with it if you know how. element IDs form the basis of how one does this

GP Michal wrote:

Thanks, Northie.  I'll do some more studying.  I really do appreciate the help.  I'm kind of curious about something.  You're the 2nd person on this forum that's used some type of software that has that familiar header with the orange background in your example screen shot.  Another person on here uses a similar orange header screen shot when he shows validation errors.  What software is this?
GP

Are you talking about something like this:

Help! I'm in a box! With an orange header!

If so, there isn't anything special going on. When you are replying and/or creating a new topic on the forums, you are given formatting options at the top of the text box.

The formatting option that creates the "familiar header with an orange background" is the [ c o d e ] - [ / c o d e ]. (Without all those spaces).