From reading Ovid's post, I think there's a little misunderstanding about Juerd's post. Juerd is referring to the fact that PM's <img> tags for clear pixels have their "alt" attribute set to "clearpixel", which messes up text-only browsers as well as screen readers (this is an issue which pops up every now and then on the Evolt mailing list).

Specifying "" for the alt attribute generally works well, and the W3C seems to think so as well:

(From http://www.w3.org/TR/html4/struct/objects.html#adef-alt):

• Do not specify irrelevant alternate text when including images intended to format a page, for instance, alt="red ball" would be inappropriate for an image that adds a red ball for decorating a heading or paragraph. In such cases, the alternate text should be the empty string (""). Authors are in any case advised to avoid using images to format pages; style sheets should be used instead.
• Do not specify meaningless alternate text (e.g., "dummy text"). Not only will this frustrate users, it will slow down user agents that must convert text to speech or braille output.

- Zoogie

-- Randal L. Schwartz, Perl hacker

Juerd: you should probably use a title like "(OT) clearpixel". The (OT) let's people know that this thread is off-topic. I use that quite a bit and so far I haven't been flamed for it :) That being said, you could use alt="" to set the text to nothing, but there are several browsers out there for visually impaired people and I suspect that they will handle that differently.

With proper CSS, you could eliminate the clear pixels entirely. Even if the gif exists, sometimes a browser will fail to load it and then you get a bunch of broken images in your browser. Very unprofessional.

Cheers,
Ovid

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I'm not quite sure if this is off topic... Please explain to me why it is.

As for the alt-attribute: browsers for the visually impaired display (through text, braille or speech) whatever is in the alt-attribute. They should not and fortunately do not say a thing when alt is set but empty. If it's not set at all, some do nothing, some display the picture's filename.
Correct CSS would indeed be a better solution.

This is what links displays:

   clearpixel
   (concentrate on your petition)                      clearpixelJoe
   clearpixel ____________________ [ searchbutton ]        perlmonks
[download]

Alt should provide alternative text for images that need it, or no text for images that are just for layout or decoration.

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$
[download]