1) In a Web site, a trap is a page that does not allow the reader to back up a previous page (the Back button on the toolbar is inoperable). A few Web site creators apparently use this technique to hold the reader and force them to read the page or to encourage them to visit other pages on their site. To exit a trap, the reader must either close the browser and open it again or enter a URL on the address line. Traps are highly unpopular among Web users.
2) In assembler language programming, a trap is a place in a program for handling unexpected or unallowable conditions - for example, by sending an error message to a log or to a program user. If a return code from another program were being checked by a calling program, a return code value that was unexpected and unplanned for could cause a branch to a trap that recorded the situation and took other appropriate action.