On Tue, 14 Sep 2010 19:01:12 +1200, Aidan Gauland <aidalgol@no8wireless.co.nz> wrote:
> 
> [1  <multipart/signed (7bit)>]
> [1.1  <text/plain; us-ascii (7bit)>]
> Is it possible to set the alt attribute of an image for HTML export?
> If I insert an inline image into an Org buffer like so...
> 
> [[./foo.png]]
> 
> ...and export it to HTML, I get something like this...
> 
> <img src="foo.png" alt="foo.png" />
> 
> But I want the alt attribute to be "foo" (or something else), not the
> filename.
> 
> I know this is an HTML-specific setting, but I still want the image be
> exported to other formats, so inserting literal HTML (see below) isn't
> really suitable.
> 
> #+HTML: <img src="foo.png" alt="foo" />
> 
> If there is no way to do this, should I file a feature request?

The following works for me:

: #+attr_html: width="50%" alt="This is a test image"
: [[file:image.png]]

(without the : obviously) and with

: Org-mode version 7.01trans (release_7.01h.501.gc19a0)