[handelaar]

It doesn't validate because breaking my preferences and opening a new window which I didn't ask for is (apart from being an obnoxious thing to do) a 'behaviour'.

The "Strict" standard, rightly, enforces a division between content (XHTML), design (CSS) and behaviour ({Java|ECMA}script).

If you want links to open in external windows, attach a behaviour to the link class with JS. Just make sure that behaviour is off by default, though, because otherwise people like me who know what we're doing won't use your site.

[dhimes]

I don't use JS on my site, because others won't use the site with JS. The link page is the only page on the site that does this, so I'm going to go with it.

It's not obnoxious if you consider that some people really don't understand how the web works or what the difference is between sites. In that case it's a convenience.

This is an idea which should be left as a "best practice," but allow for reasonable differences.