Help - I've lost the "basic layout menu "

As this page is not user editable and pretty much hardcoded, it's very hard to lose a part of it. Please check if the menu really isn't there or if you just can't see it (view the XHTML source). I suspect you forgot to close a tag in your mainskin or something like that. One indication for this is that the validator finds lots of closing tags which are 'not open' before crashing in disgust.

Since when do you notice this? Have you changes something yourself before it happened, or could it be a change in a default skin? By the way, the default skins are now all XHTML 1.0, so if you want your page to be HTML 4.0, you must customize all skins. You currently have a lot of XHTML tags in your pages.