Meaning of log output

[edulid]

Hello,

as I said in my previous post (http://forums.smartclient.com/showthread.php?t=15607) I got these javascript log output:

19:20:33.619:INFO:Log:initialized
19:20:33.930:WARN:AutoObserver:Use addInterfaceProperties() to add methods to interface [Class AutoObserver]
19:20:34.323:WARN:Log:New Class ID: 'IAutoFitButton' collides with ID of existing Class object '[Class IAutoFitButton]'.  Existing object will be replaced.
19:20:34.323:WARN:Log:New Class ID: 'HeaderImgButton' collides with ID of existing Class object '[Class HeaderImgButton]'.  Existing object will be replaced.
19:21:00.198:INFO:Log:isc.Page is loaded

I already solved my problem, but the logs are still there...
could please someone tell me what does the message mean?:
19:20:34.323:WARN:Log:New Class ID: 'IAutoFitButton' collides with ID of existing Class object '[Class IAutoFitButton]'. Existing object will be replaced.

Thanks!