If you’re a good web designer (or just one who cares about his Google ranking) then you’re populating your IMG elements with the alt attribute (tag). Sometimes this is easy, like when you’re describing a picture in a new story. Sometimes, however, you’re using an IMG element because you’re overcoming some stylistic problem with using plain text – in other words, you’re using an IMG for text content. A good example is on the BBC News website. Here’s the (edited) code:
<a href="http://www.bbc.co.uk"><span>British Broadcasting Corporation</span> <img src="light.png" alt="BBC" /><span>Home</span></a>
If you’re sighted you’ll observe on the actual page that you see none of the words “British Broadcast Corporation” or “Home”, just the BBC logo as an image in the top left, and as normal you can click on it to go to the BBC home page, so it looks neat and simple. What’s the extra text for? We can surmise that if you’re using a screenreader or other AT device you might, depending on the AT, hear “British Broadcasting Corporation BBC Home”, which may be more helpful than just “BBC”. Let’s assume that’s the idea.
The problem is that in the absence of any visual positioning, and without any CSS instructions to add spaces into the code, what you’ve actually coded when the IMG element is directly replaced by its alt attribute is this:
<a href="http://www.bbc.co.uk"> British Broadcasting CorporationBBCHome</a>
If you run that into a speech synthesizer you’ll probably hear something like “Broadcasting Corporation-buh-buh-chome”, which isn’t what you wanted!
The problem is that there aren’t any spaces in the text that results from swapping out your IMG element with its alt attribute content. Sure, the AT could guess that you wanted to have spaces, but then it’s changing your content – and you’ll quickly run into a situation where adding spaces in breaks up other words when it shouldn’t, like sites that use IMG elements to produce fancy initial letters on the first words in paragraphs. What you should do is something like this:
<a href="http://www.bbc.co.uk"><span>British Broadcasting Corporation </span> <img src="light.png" alt="BBC" /> <span> Home</span></a>
or this:
<a href="http://www.bbc.co.uk"><span>British Broadcasting Corporation</span> <img src="light.png" alt=" BBC " /> <span>Home</span></a>
In other words, structure your alt attributes so that your content still makes sense when the IMG element is replaced by the alt attribute content. Simple, but easy to overlook.