A little mystery SOLVED
Another mystery was that a folder I had excluded from Time Machine backups on the old machine was not included in the transfer.
Joe Kissell from TidBITS solved both mysteries at once: I had selected the Time Machine backups disk as source instead of the main disk on the old Mac! When migrating there were two sources with the same name, and I just selected the first one without thinking much about it. That's a flaw in the Migration app: it should indicate which is the T.M. back volume and which is the main disk.
OK, here is a little mystery for the computer-savvy amongst you:
Thursday about 18.00 I updated the home page and related files on my commercial site. After having done that, I set up my new computer, and started it on the long, automatic process of transferring all my settings and file from the old computer.
And today, when I opened those pages/files on the new computer, they looked as they had looked before the update on Thursday! They had the pictures and text I put on them Wednesday evening. But how the heck is that possible? The files were changed and saved, otherwise I could not have uploaded them. And on the web site it was clear that I had updated them.
I have booted up the old computer, and on that machine the pages do appear like after the Thursday update. So how did the Migration application go back in time and get the pages as they looked hours earlier? Any ideas at all?