What's up with my cactus?

[Creature]

Hi everybody,

I'm really not that green-fingered but I have recently been given a cactus and am anxious not to kill it (not least because I'm told it's quite difficult to). So I brought my cactus home, stuck it on my windowsill, and a few days later I noticed it has some brown discolouration on the side facing the light. I swivelled it around, and when I went to water it yesterday the side that was facing the window was a rather nice green. I don't think it was the light that harmed it, but the weather's been a bit more overcast lately so perhaps that protected it. Anyway, what have I done to this poor cactus?

There's a picture of it here:

on what kind of cactus I've got, how often I should water it (I've been giving it some once a week), and other such cactus care tips would be gratefully recieved too.

Thanks,

[Phisherman]

You are probably over-watering the plant which is the fastest way to kill a cactus, especially without sunlight. Do not fertilize at this time.

[Creature]

After my watering yesterday it's certainly looking a lot less healthy today, so I shall not water it for a while and see if it improves. How often should I be watering it?

Thanks,

[Salty Thumb]

Creature wrote in news:c7qpv3$no9$ [e-mail]:

don't know what's wrong with the cactus, but it looks like the pot is leaking a human head.