Sorry, really not sure what to do about that.

The file xml/subsilver2.xml

Make sure the cookie path is set to '/'

It's one of the edits you do to functions.php I believe.

You missed the edit to breadcrumbs.html

Open the board3 zip file, copy all folders from root/style/subsilver2 to /public_html/portal/styles/Macinscott_3

It's not a problem with the portal, the style just uses an odd font for the body text.
Change it by editing one of the CSS files under theme

Your columns still arn't right.

ACP -> Styles -> Themes -> yourstyle-> Refresh

No problem, check you haven't got any other files missing.

I've got it looking like http://tcoa.co.uk/test/portal.php?style=3 is that what you're aiming for?

Kev to the rescue! Unfortunately I've only ever run apache personally so I'm at a complete loss.

Please go to "ACP -> Styles -> Themes -> Prosilver-> Refresh"

have you got the portal.php file on your server? As this error appears when you try to access a non-existing php file. e.g http://idzen.dk/phpBB3/toast.php

Make sure http://idzen.dk/phpBB3/portal.php exists.

Sorry but design really isn't my thing.

It's to do with the CSS. Make completely sure you've done the edit regarding "styles/prosilver/theme/stylesheet.css" then go "ACP -> Styles -> Themes -> Prosilver-> Refresh"