1. A method for parsing a markup file, comprising: parsing a first portion of the markup file with a lightweight parser in a computer system, the lightweight parser being capable of performing a first set of parsing tasks; parsing a second portion of the markup file with a heavyweight parser in the computer system, the heavyweight parser being capable of performing a second set of parsing tasks, wherein the first set of parsing tasks is a subset of the second set of parsing tasks; and transitioning between the parsing of the first portion of the markup file with the lightweight parser to the parsing of the second portion of the markup file with the heavyweight parser upon an occurrence of a transition event.