re:
!> Ok pay attention! I've I explained earlier, I've already set my
!> web.config file, manually, with the appropriate text:
!> <compilation debug="true" strict="true" />
No. *You* pay attention. I've already explained it's a *bug*.
It's been fixed in VS 2005 SP1.
re:
!> It's not having any effect.
This isn't an ASP.NET bug. It's a VS 2005 bug.
Nothing you do, as far as ASP.NET configuration goes,
will affect the way VS 2005 compiles source files.
What you *can* do, and works, is install VS 2005 SP1.
*Then*, when you change Tools/Options/Projects and Solutions/VB Defaults to
option strict on, and you change the web.config to strict="true", and you add to a .vb file :
Dim NiceBug As Boolean = "Hello world"
....you will see that the VS 2005 IDE flags it as an error,
and suggests you change the line to : Dim NiceBug As Boolean = CBool("Hello world")
Never mind that the suggested change is bonkers, though.

At least it flags the error as an error which will not compile correctly.
re:
!> Have you tried Tools, Options, Projects and Solutions, VB Defaults?
!> No idea if this will modify existing projects, though, as I never go anywhere near VB.NET...
It doesn't even change the setting for *new* projects, Mark.
re:
!> where is it changing the setting, and can I not set it myself manually?
There's no way to change the setting at design time, for new projects,
because the change is needed in the project *template*.
Devenv.exe creates a new project based on the existing templates,
and the default for that is option "strict= false".
Changing the option, in the template's web.config, is the only solution.
Btw, the directory location in my earlier post is either incorrect or was changed by SP1.
Instead of :
drive:\VStudioInstallDir\Common7\IDE\ProjectTemplates\VisualBasic\Web\1033\WebApplicationProject.zip
The correct path is :
Drive:\VStudioInstallDir\Common7\IDE\ProjectTemplates\Web\VisualBasic\1033\WebApplication.zip
Extract web.config from that zip file, change <compilation debug="false" strict="false"
explicit="true" />
to <compilation debug="false" strict="true" explicit="true" />
and zip it up again, updating WebApplication.zip
That will automatically create/compile projects with that strict="true" configured.
Ok pay attention! I've I explained earlier, I've already set my
web.config file, manually, with the appropriate text:
<compilation debug="true" strict="true" />
It's not having any effect. Therefore fiddling in zip files is going
to have the same effect next time I create a new project - no effect
whatsoever. The only thing which makes a difference is setting the
option at the top of each page. I appreciate that this isn't a
problem in c#, but this doesn't help me as I'm not developing in c#.