[Ur] A direction for Ur/Web

[Adam Chlipala]

Karn Kallio wrote:
> I assume safely tweakable themes require some sort of guarantee that there is
> at least a minimum level of correspondence between the CSS and the XHTML.  The
> current mechanism of linking to a style sheet provides no guarantees on the
> CSS content of that style sheet; indeed, the style sheet may not even contain
> valid CSS.  Of course Ur/Web supports theming, but I don't think it currently
> supports *safe* theming.  Control of CSS class attributes via style helps but
> leaves too much underspecified to be safe (in my opinion).
>    

If it's "safety" you're concerned with, I believe that can be achieved 
just by limiting which URLs may be included in CSS.  There are other 
properties within valid CSS that could cause _annoying_ behavior, but I 
don't see that as being an issue for allowing someone to theme his blog 
or CMS.