A class-action lawsuit filed against Taco Bell claims that the beef the restaurant-chain uses doesn’t meet minimum federal requirements.  Lawyers who filed the suit on behalf of a customer say the meat was found to contain a very small amount of beef.  Taco Bell says its advertising is not misleading and denies the accusations.  "Taco Bell prides itself on serving high quality Mexican inspired food with great value," said Rob Poetsch, a Taco Bell spokesman.  "We're happy that the millions of customers we serve every week agree. We deny our advertising is misleading in any way and we intend to vigorously defend the suit."