launch url and then close

[jbv at souslelogo.com]

Hi list,
On desktop, when a browser window is opened outside
of LC using the "launch url" command, is there a way
to close the browser window after a while from the
LC script ?
I am not talking about the revbrowser, but the actual
default browser.
I guess the answer is "no", as I haven't found anything
in the doc nor in the forum, but I'm asking anyway.

And second question : when a URL is used in a revbrowser,
the default browser is used by LC, but does it use the
same http header as when the same url is entered in the
address bar of the actual browser ?

Thanks in advance