I know what the coding is.  It's also more commonly referred to as
"inline-coding".

Some will tell you that it's perfectly fine and others (like myself) will
tell you to steer clear of it as it creates a jumbled mess (called
"spaghetti code") that is difficult to troubleshoot (as you are finding
out).  This was the only way to write server-side code back in what we now
call "Classic ASP", which was about 7 years ago. Now, we have a choice.

IMHO, there really isn't any reason to EVER write code as you've shown
below.  It can all be written separately from your actual page content.

As for your original question, I believe I answered it when I said that I
don't believe your conditional inline-code can be used with user controls in
the way you are trying to use it.  I believe it has to do with the order in
which the controls are rendered vs. when your "if" logic is being processed.

You may want to consider a good, old-fashioned browser re-direct to a page
that has the appropriate user control on it based on the browser you've
sniffed.

-Scott