Why do spiders hang upside down in the middle of their webs?

I get a lot of spiders webs in my garden and without exception, when the spider is in the centre of its web, it is orientated with its head towards the ground - is there any particular reason for this? I can think of at least one reason NOT to adopt this position - the spider cannot see birds flying in that might regard it as their next meal.

Why do spiders hang upside down in the middle of their webs?
Yeah - most day-hunting spiders that hang in the center of the web prefer the head-down position. Not all do; there are at least a couple that hang head-up in the center of the web, but I'm guessing you're English, and I don't off the top of my head know of any European spiders that might be head-up. We're talking only about orb-web makers, by the way, right? As to why, it beats me - perhaps there's some physical explanation, but then you'd expect the very heavy abdomen to be downward. Personally, I would guess that it's related to the fact that they hunt in the day like that - the abdomen may be acting as a warning to hungry birds that this is not an appropriate meal (presumably there's some defense there against birds), or it may be warning the birds that there is a spider web there that they shouldn't fly through. Lots of very interesting science has been done by interested amateurs who decide to explore questions like this - why not join the ranks of Fabre and Darwin and go into this further?
Reply:if they were on top then there prey would see them
Reply:BOO-HOO....GET A GRIP....STOP WHINGEING....GO HOME TO YOUR PARENTS AND GET A PROPER JOB.....yes, this is me replying to your message with the very answer that you left on mine. For your information, my question was on serious issues that are effecting my life and i dont need sad little old men like you leaving bitter and twisted answers that are in no way, shape or form of any help to me or anyone else for that matter. I feel its a shame that old farts like you have to sit on here writing shitty little messages just to make their own sad little lives seem a little more worth while. I am amazed that you say 'get a proper job' when im completing my degree and have many career aspirations, i also feel i should point out i was not whingeing....my problems ARE real and ARE worthy of appropriate and worthwhile answers...seemingly unlike yours mr 'why do spiders hang upside down in the middle of their webs'. You get a grip!
Reply:Gravity, they are being pulled that way. Check it out, all their legs will be higher than the main part of their bodies, more grip and stability.
Reply:Not all spiders sit in their web. Some spiders actually sit away from their web on a thread of silk with a "trigger" line attached. When the web vibrates this lets the spider know something is in its web and it swings across like tarzan.
Reply:sorry, I saw your avatar and I thought you were someone else for a moment. But you're not. Too bad.