站着说话不腰疼的意思。

你能你就上，不能别在这里叽叽歪歪

你行你上，不行别BB 具体的意思就是：你如果能做这件事就去做，不能就别在这说废话 BB是表示一种很惹人讨厌的说话行为

The meaning of this sentence is that if you have enough ability of doing something , just go and doing it right now! Otherwise " please stop bullshit"

Chinese internet slang :P It means: Do it yourself and show us, if you can. Otherwise, shut up if you can't. It is a word-for-word translation from a Chinese version, which you can find in the previous replies. People use it to reply to harsh critics (sometimes attacks) on someone's performance, abilities, etc. Btw, there are many similiar 'creations' on Chinese internet. I think people made up those expressions for fun.