Marilyn Tavenner, chief administrator at the Centers for Medicare and Medicaid Services, testified before the U.S. House Ways and Means Committee today.

According to her written testimony, she told the committee there have been more than 20 million unique visitors to the website since Oct. 1.

“Unfortunately, the experience on has been frustrating for many Americans. Some have had trouble creating accounts and logging in to the site, while others have received confusing error messages, or had to wait for slow page loads or forms that failed to respond in a timely fashion,” she said.

“The initial consumer experience of has not lived up to the expectations of the American people and is not acceptable. We are committed to fixing these problems as soon as possible.”

Click here to read more about how her apology was received by the committee.

Tomorrow at 9 a.m., Health and Human Services Secretary Kathleen Sebelius will testify to the House Energy and Commerce Committee. That hearing will be webcast at