i want to travel to u.k. were i have to appliy for a visa in usa?

can i get a wed site for unitedkingdom visa office

all you need is a passport to travel in the UK , you can apply at select u.s. post office sites.

If you are in USA on student/authorized work permit visa, you need to locate the UK embassy/consulate office, which serves your area of residence.
A rough list of documents reqd are: passport, travel itinerary, proof of hotel acco/invite letter from friend/relative etc, bank statements etc