You may find that they state that all products using LCD screens are subject to upto 3 dead pixels however a friend of mine who works in trading standards was telling me how even though this may be the case you still have a right to send the item back and get a refund.
If you decide to keep the netbook, there are various ways you can sometimes re-enable the pixel.
This depends if it is stuck or dead.
Lightly pressing on the screen is one option but the one that worked for me was a little batch file that flickers fast random colour changes. Drag the window over the dead pixel for a few seconds and it can sort it out.
More info here:
http://www.instructables.com/id/SG16CDVFABRX1UN/