Tapestry templates contain a mix of the following elements:
Static HTML markup
Tapestry components
Localized messages
Special template directives
Usually, about 90% of a template is ordinary HTML markup. Hidden inside that markup are particular tags that are placeholders for Tapestry components; these tags are recognized by the presence of the jwcid attribute. "JWC" is short for "Java Web Component", and was chosen as the "magic" attribute so as not to conflict with any real HTML attribute.
Tapestry's parser is quite flexible, accepting all kinds of invalid HTML markup. That is, attributes don't have to be quoted. Start and end tags don't have to balance. Case is ignored when matching start and end tags. Basically, the kind of ugly HTML you'll find "in the field" is accepted.