We can only interpret recent moves by Tribune Co. as mixed signals. On Monday it was reported that the Chicago Tribune and Chicago Public Schools this fall will introduce a weekly publication (and complementary Web site) called “The Mash.” The newspaper is targeting roughly 100,000 high school students in the Chicago area. The report follows comments last week by Tribune boss Sam Zell that he intends to shave 500 pages of news each week from the company’s dozen newspapers, including The Chicago Tribune and The Los Angeles Times. The cuts at Tribune once again beg the question: how long can newspapers survive the accelerating migration of readers and advertisers to the Web?