ESTA is an automated system that determines the eligibility of visitors to travel to the U.S. under the Visa Waiver Program. The ESTA application collects the same information collected on Form I-94W. ESTA applications may be submitted at anytime prior to travel, though it is recommended travelers apply when they begin preparing travel plans.
Since Sep 8, 2010, the US government is charging $14 for the ESTA authorization.
Applications are only accepted via the ESTA website at the following address: https://esta.cbp.dhs.gov