...not to be a part of the mobile portal.

[Gingerbread Man]

"Sorry!
An Error occurred. Please click a link in the navigation at the top of the page to continue.
There has been a problem with content generation. The page you requested seems not to be a part of the mobile portal."

Why's this then and what can I do about it?

I get it when following links to other Pistonheads pages, I think from memory that it has been to classified adverts.

[RacingPete]

If you change the mobile part of the web address to www then it will show the page.

Though not sure what section it is in, so if you replicate the problem let us know and we will look into it.