If you're using the Html Agility Pack embedded XSLT tools, you're facing two hard Html Agility Pack limits (at least with version 1.3.0.0):

• Support for Namespaces is limited
• The XPATH implementation does not support navigating to the attributes (only selection). This XPATH "//tag1/tag2/@myatt" does not work for example.

You can overcome these limits with C# code, but not easily with pure XPATH, hence not with XSLT.

In these case, it's often easier to convert the HTML to XML using the Html Agility Pack, and then use a regular XSLT on XML with the standard .NET classes, instead of XSLT on HTML with Html Agility Pack classes.