Online colleges are the fastest-growing segment of higher education despite questions about their quality. More than 2.3 million people took at least one online college course in 2004, according to one study - a 47 percent jump from 2002. And now, thanks to an act of Congress last week, the door to an online college education is expected to open wider. Colleges no longer will be required to provide at least half their classes on a physical campus to qualify for federal student financial aid. While two-thirds of traditional colleges and universities now offer online courses, the policy change is expected to be especially helpful to those mostly for-profit schools that offer all of their instruction online.