That is a wonderfully succinct answer from Tartan! If you click here, that will link you to a web-page which explains in a bit more detail, if you need it.
it was wdiely believed that when the box was opened all the evil that existed would be unleashed into the world, and evrything would be reversed. ie inside would become outside, order would become chaos.
I think Pandora did know what was inside, but being a curious female she couldn't resist the temptation to peek inside. Had she actually resisted and not opened the box, she would have spent the rest of eternity nagging some poor man to do it for her!
If it had have been a jar, she
a) Would have had to ask the nearest man to open it;
b) Probably would have opened the gherkins by accident; but
c) Wouldn't have been able to reach it from the cupboard in the first place.
Oh no, you have released all the gherkins of the world...