I would like to add a TOC entry that linked to a registration website is this possible or ist the another way to get a webpage to lauch from within the presentation?

You don't tell if you are using Captivate for this goal, and which version you are using.

If it is Captivate, did you try to insert a web object? It is under the big button 'Objects'.  Or you can use the command 'Open URL' triggered by any event.

This isn't the product technical support forum.  It's the Lounge. 

Which Adobe product are you using?