Go to References and remove reference to DropDownCheckList. After that
click add - browse and point to DropDownCheckList.dll from \bin
folder. Also, ensure that DropDownCheckList.js is located in /
aspnet_client/UNLV_IAP_WebControls/DropDownCheckList/ directory. This
is mentioned on Page1.aspx, otherwise you will get a js-error on every
page.