The mystery unfolded – the molecules have been (and can be) found

I think this was delayed by WordPress.)

1. Jean-Claude and his students cracked a bit of it. Egon has explained it fully and provided the motivation…
   
2. Egon Says:
   October 14th, 2006 at 7:55 pm eI have not been able to track down all of the involved blogs, but my final guess would be that these molecules are taken from chemical blogs. The first one is from tenderbutton, the last one already recognized by J-C (thanx for the tip!).(Peter, please don’t say I’m wrong…

Yes – they are from the blogs I mentioned – Useful Molecules, Totally Synthetic, Org Prep Daily, and Tenderbutton. The second posting was the very fisrt molecules on those blogts; the third was the most recent molecules (which were also in PubChem so I could copy the images).
The other theme (which some people hinted at) was that the molecules had InChIs. These were concealed in the alt attribute of the img so they weren’t visible to humans. Paul Docherty (Totally Synthetic) droped in for a chat last week and I showed him GoogleInChI. He was interested but worried that the InChI would take up too much space on the page. I first tried hiding it in:

<spane style="display:none">InChI=...</span>
InChI=...

in the first molecules but I was advised that Google doesn't like non-displaying information. So in the second batch I hid it in the alt attribute and this seems to work. (Unfortunately WordPress seems to corrupt handcrafted HTML on images and some of the alts got overwritten, so that is why the earlier molecules didn't all work).
So the main message is that if you put InChIs in alt attributes, Google will index your blogs. This means that we have chemically aware blogs for the first time. If all the blogs do this we shall have a de facto chemical knowledgebase.