tributes may
provide some opportunity for examining the configuration of a user agent's host
environment. <a>'requiredExtensions'</a> by determining whether custom
extensions are supported by the user agent. <a>'systemLanguage'</a> by
determining the preference of one language relative to another.
</p>
</dd>

<dt>
Interoperability considerations:</dt>
<dd>
<p>
The published specification describes processing semantics that dictate behavior that must be followed when dealing with, among other things, unrecog