We, as website makers, quite often advise our clients to avoid generic link text (read more,click here, etc.), and explain that more verbose descriptions help give context to users with screen readers. But using semantic link descriptions actually helps everyone.
Simply defined, aboutness is the quality of meaning; what something is about is defined by its aboutness. To extend an example from Morville’s book, let’s regard a web page which contains W.H. Auden’s poem, Funeral Blues:
He was my North, my South, my East and West,
My working week and my Sunday rest,
My noon, my midnight, my talk, my song,
I thought that love would last forever; I was wrong
Although we know that the poem is about death, the word itself doesn’t appear in the poem; so how could a search engine that indexed the page know what it was about, and return it in the results of a search on that topic?
In order to gain some context, the search engine will look at the text of the links to that page*; so a link with the text ‘read more’ will provide no context whatsoever, whereas a link with the text ‘W.H. Auden’s poem about death’ provides aboutness.
And it’s not just for our link text that semantics are important; the same principle applies with HTML – your markup gives aboutness to your content. So if you’re a front-end coder, be sure to at least use appropriate container elements (the HTML5 Doctor can help with this), and if you want to go further take a look at the likes of Microformats and RDFa.
* Search engines look at more than this, of course, but this is the most obvious example.