Mark_A - 3:13 pm on Jun 17, 2010 (gmt 0)
Indeed, at one point there was a frowning on 1x1px transparent gifs because people were keyword stuffing the alt text and getting a result from it.
I thought it was a great shame as I used 1x1 transparent gifs a lot as spacers and shims and the like. Mind you I never associated any alt text with them! :-)