Since a few months, travellers to the US need to get an online pre-approval from the US Department of Homeland Security (DHS) before the airline can accept them on board. This approval is given here by ESTA = Electronic System for Travel Authorization.
Is not really a problem - is for free (at the moment at least) and usually gives an immediate approval/authorization number, which one needs to bring then to the airport when checking in.
When I was ready to do this, I noticed that there are many ESTA sites on Google, and they all look very official. First I landed at www.esta.us and was surprised to find there a fee mentioned ($49.95). Also the site www.esta-online.co.uk charges a fee (£20.00), and so does www.estauk.com ($45). As I have found out from other bloggers, these sites are scam! They may work and actually give you a valid authorization, but they are ripping you off - you need not to pay any fee for this service! (Therefore, I did not put a link under those sites here in this blog entry).
So in case you plan to travel to the US and need the ESTA authorization, only go through this site: