"One of the other key issues we ran into was that we needed to improve search and navigation," said Bert DuMars, director of the IRS Electronic Tax Administration. "We also had increasing volumes of use -- this year we passed 178 million visits, [and] we had over 1.2 billion page views of the Web site. During the filing season, this is a top 50 Web site, and even in the nonfiling season, it's still very heavily used. The data is very complex, and it's hard to understand sometimes. Our goal is to try and make it easier to comprehend and easier to get to."

Coffin said that e-mail responses to the site were mixed but that the agency had not seen a "precipitous dip" in user satisfaction. The customer satisfaction index showed a slight trend upward in the first several weeks after the new site went live, he added.