Insider trading is hard to prove. To be convicted, a person must have bought or sold a stock based on material information that is both unknown to the general public and likely to have had an important effect on a company's stock price.
Traditionally, companies have made major announcements before or after the close of trading so that all interested investors and analysts are apprised of the news before trading resumes in their stocks.
Generally, a rally will have staying power, technicians say, if, in addition to price movements, it has heavy trading volume and breadth, meaning that several stocks rise for each stock that falls.