Mine froze!!!
It displayed a message asking "Stop running this script. A script running on this page is causing your web browser to run slowly. If it continues to run your computer might become unresponsive.". I click on Yes then everything returns to normal!!
Possibly there's an infinite loop on the page :)
I am using following version:
IBM Lotus Domino Designer 8.5
Release 8.5.2
Revision 20100811.1131 (Release 8.5.2)
Standard Configuration