Although the overall audience for broadcast television programs continues to decline, at least some of the departing viewers may be catching the programs on their computers, a survey by ABC indicated Monday. The network said that the audience for episodes of its primetime shows posted on line reached an all-time high in May, jumping 53 percent over April. (The network aired numerous season and series finales in May, which No Doubt accounted for part of the viewership increase.) The audience for programs posted on ABC.com has more than doubled over the past year, the network said. "Clearly, the demand for ABC's high quality television programming continues to grow online, particularly among younger viewers," Albert Cheng, head of Disney-ABC-TV Group's digital media unit, said in a statement.