Yes, it's possible.
For basic HTML View customization, you have to possess knowledge in HTML and XML. The advanced HTML View customization may require XSLT and JavaScript experience. For further details, please take a look at the HtmlView folder located in "C:\Program Files\Common Files\Softerra Shared\LDAP Administrator 3" for LDAP Administrator 3.x and C:\Program Files\Softerra\LDAP Administrator 4" for LDAP Administrator 2008.