According to the Department of Homeland Security and by the end of the summer, the use of paper I-94W forms will be eliminated for VWP travelers with an approved Electronic System for Travel Authorization at all airports. The green colored paper I-94W record will soon no longer be issued by the US Customs and Border Protection inspectors.  

As of January 12, 2009, all nationals of VWP countries have been required to apply for an ESTA (Electronic System for Travel Authorization) prior to boarding a carrier to travel to the United States. Please note, however, the ESTA requirement does not apply to those already in possession of a valid US visa.