Hi Claude IMBERT,
I was not able to reproduce the issue. If I call the Select method on a webbrowser when I select its corresponding tab, I always get a focused webbrowser. However, if I do not call the Select method, I always get unfocused webbrowsers on tab selection. I have attached a sample project to demonstrate this behavior.
If you have additional questions, do not hesitate to contact me.
the Telerik team