Mk III Astra 1.6 Petrol Engine Management Warning Light

Was driving my car yesterday travelling at about 40 mph and an orange
warning light came on (looks like a little engine with a lightning bolt in
the middle). I'm assuming this is something to do with the engine
electronics/management...?
There was no apparent change to the sound of the engine, or the 'feel' of
the car, but I pulled in a couple of miles later, and turned the engine off
for a few minutes. On restarting, the light didn't come back on.
What sort of problem is this light alerting me to, and is it something I
should worry about, assuming it doesn't come back on again? Or even if it
does?

[ Doubt it is relevent, but last weekend, I had a problem with the
alternator belt, a narrow section frayed off, and I had to cut it away, so a
part of the alternator belt is currently about 4/5 its normal width. (I'm
planning to get that changed in the next day or so) ]

 

Even Vauxhall admit in the user manuals that the light might come on
occasionally for no good reason; so don't worry. I fit starts
happening more regularly then you need to get the codes read by an
auto electrician or using the 'paperclip method' which I think should
work on a mk3 Astra.

http://www.cavweb-forums.co.uk/showthread.php?t=173819