Over-use of 'alt'

[shesays]

Can someone tell me the uses of the alt tag? I know it is used to give alternative text for an image or link, but is there a 'good' amount of words you should use?
I have seen on a website for a popular UK high-street shop an idea I thought was quite good from a sales point of view but not sure if it is a good idea from a coding POV.
They have an extensive description of what the customer will find in each category, not just the usual 5 or so words!

What do you think?
I am interested in your views.

[lo0ol]

The thing you probably will worry most about alt attributes is that of screen readers. Alt attributes should serve as a replacement for your images- so imagine, no, you can actually do this- go to your page with your images turned off and theoretically, with help from your alt tags, you should still have a good, general idea of how the site works. It's not a true test, since you can still see formatting and positioning (obviously a screen reader just reads it off), but it gives you a bit of an idea.

As for the length- verbose alt tags probably aren't needed; for most things you can sum them up pretty quickly. Title attributes, at least from what I've been able to gather, go into a little bit more depth regarding a particular element than do alt attributes. But feel free, anyone, to correct me if I'm wrong on this, since I'm not all too up-to-date on my accessibility knowledge as of late.

[vgarcia]

Rules of thumb for image descriptions:

Alt attribute: short and to the point, describe what the image is in 80 or less characters

Title attribute: extra information that isn't essential for understanding but may help create a more vivid mental picture. Usually between 80 and 1000 characters.

Longdesc attribute: this is a separate document (usually an HTML document) that you link to that gives full detail of the image. Write as much as you want but don't overdo it

[zcorpan]

The amount of words should be as much as you need to represent exactly the same meaning as the image. There's no upper limit. Don't describe the image with the alt attribute; provide an alternative to the image.

For instance, what alternate text do you provide for your site logo that says "Sitepoint"? Don't describe the image (alt="Logo"), don't use additional information (alt="Empowering Web Developers Since 1997"), use simply what you mean with the image, in this case, alt="Sitepoint".

[AutisticCuckoo]

Here's a good starting point: The Alt and Accessibility.

[studiobluemedia]

Hi shesays - I just wanted to interject into this alt conversation. What you need to keep in mind and I don't catch this in the replies above, except in a basic way(sorry guys) this is most important- is that in order for the web page to be truly accessible to someone who can't see and is having the site read by an alternative browser, you do have to have a concise description of what the image is. I suppose you may be thinking - what? The web being such a visual tool - what would a visually impaired person possibly get out of the experience? Well, Mr. Berners-Lee wanted the web to be available to all users and hoped that it could be the great leveler.
The site that AutisticCuckoo listed above is a good start-but even that does not get into the ultimate reason for alt tags until the user comments.
I think if you keep in mind the reason for the alt tag - so that an impaired user can hear what the picture is - it will help you devise your wording. Perhaps the shop is not so offbase in their extensive descriptions.
I would also recommend this site for good info on accessibility: http://www.w3.org/WAI/

Also http://webxact.watchfire.com/
and
http://watson.addy.com/
These sites offer a web page checker for accessibility issues.
I think as our technologies continue to progress we will see the levelling of disabilities and non-disabilities when it comes to the web. My opinion is that the savvy web developer will embrace accessibility and utilize the necessary tools to make their sites accessible to all users.

The power of the Web is in its universality. Access by everyone regardless of disability is an essential aspect.
-- Tim Berners-Lee, W3C Director and inventor of the World Wide Web

best of luck,
blue

[bpeh]

yes, i always write what i think I want the user to see if the images are not displayed. alt tag can also be effective for seo.

[shesays]

Thanks for all your replies and links. It can get very confusing so I suppose it requires a good measure of common sense as well

[someonewhois]

I always go on the basis of what information is the image trying to potray. If that image were to be dead (ie. the viewer was blind or the link got messed up), I want a textual representation of that image so that it makes sense the same as if it was an image.