For reference: To implement a tool tip you should officially be using the title attribute. This is valid and is picked up in all browsers - not just IE. If you want to include tooltips, most images would require both an alt attribute and a title attribute. Sometimes this is the same text for each, but often it’s not, as tooltips and alt attributes clearly have very distinct functions.

Typically, Microsoft doesn’t follow the rules correctly with alt, but thankfully it does implement title attributes correctly where they are present. For example, giving an image an empty title attribute will override the default use of alt text for tooltips in IE. That way, not even the “tiny yellow tooltip” referred to above would appear for images with an empty alt attribute.

For purely decorational images therefore you could use a blank alt attribute AND a blank title attribute to ensure it’s accessible, valid and also IE-friendly.

Of course you should ideally be supplying purely decorative images within the CSS anyway. Here, naturally, images do not need alt or title text.

Hopefully that helps clear up an oft-overlooked IE irregularity.

A picture of Patrick Moore with a chart showing planets behind him, and him pointing to Jupiter. If the fact that he is pointing to Jupiter rather than another planet is important to the understanding of the page then that should definitely be conveyed within a text equivalent.

After all the additional image conveyed - what he looks like - isn’t conveyed by saying “here’s a picture of Joe Bloggs”.

You’d need to add “he’s wearing glasses, he’s got dark hair and bushy eyebrows and…” by which time your listener would be telling you that they really don’t care.

Surely if the text indicates elsewhere that Joe Bloggs is a director, then this sort of image is bordering on decorative?

And “space” alt text will only show up as a tiny yellow tooltip if you’re using internet explorer (I know that could be inferred from what went before about IE, but thought it might be worth re-stating that this would only be IE)

Having said that, I agree wholeheartedly on the rest of it, but you’d already know you were preaching to the converted with me anyway!