I want exchange my 250 usd on skrill for bitcoin 240 usd.
I just posted this in another thread, but - given that Skrill's transactions are reversible (like Paypal and others), I don't think you'll get a lot of interest in this offer. Also, they apparently don't like people using their service to trade bitcoins and can block your account if they catch you doing it. See more information here:
https://en.bitcoin.it/wiki/Payment_methods.