PSGML can highlight the markup giving the markup a different face
(see section `Using Multiple Typefaces' in The Emacs Editor).
The highlighting will only be done if the variable sgml-set-face
is non-nil. The default settings make tags bold and comments
italic, but this can be modified with the variable
sgml-markup-faces. When highlighting is on PSGML will parse after
every command until the whole buffer has been parsed or user event
occurs.
To remove the highlighting type M-x sgml-clear-faces.
User Option:sgml-set-face
If non-nil, psgml will set the face of parsed markup.
User Option:sgml-markup-faces
A list of markup to face mappings.
Each element looks like (markup-type . face).
Possible values for markup-type is: