Error handling

[Kroc]

There's no error handling of any kind.

I need to decide carefully what should be a notice / warning / fatal as external use of DOMTemplate in a templating system may purposefully run non-matching XPaths (e.g. translation strings in NoNonsenseForum). In general, non-matching XPaths are a non-issue, invalid XPath strings are fatal and HTML fragments that fail to load / attach should be a warning (since user-provided content may be invalid XML in certain CMSes)