Error: Unkown Server Tag DayPilot, how should I correc it?

Hello everyone! I downloaded the VS 2008 express and the DayPilot lite, I started a new web site project and linked the DLL file to the Toolbox like the tutorial said.

I then dragged and dropped a DayPilot calendar to my design view and I can see it render there with only one column (today's date). But when I run the project I get an "Unkown Server Tag" error for DayPilot on the line that says

<DayPilot:DayCalendar

any idea what I should do to fix this?

thanks in advance!