U.S. District Court Judge Thomas Penfield Jackson has ruled that Microsoft Corporation violated the Sherman Anti-Trust Act by using its position in the Web browser market to “the detriment of competitors.” The judge also found that Microsoft could be liable under state anti-competition laws. Judge Jackson must now schedule hearings later this year to consider remedies for Microsoft’s actions, which could include structural changes to the company, business restrictions, or an actual breakup of the company. Microsoft has repeatedly said it would appeal any ruling against it in the anti-trust proceedings; experts estimate the case could easily drag out to the year 2002. Microsoft stock was down nearly 15 percent in anticipation of Judge Jackson’s announcement, dragging the NASDAQ index down 7.63 percent in its largest single-day point decline in history. The text of Judge Jackson’s ruling is available from the U.S. District Court of the District of Columbia’s Web site. You can also check out TidBITS’s coverage of anti-trust issues regarding Microsoft.