By default, the Front End Application will detect if the end-user has the Viewer installed on their system. If you know that none of your users have the Viewer, you can improve performance by disabling automatic detection.
<init-param>
<param-name>disableViewerDetection</param-name>
<param-value>true</param-value>
</init-param>
The disableViewerDetection setting is not a documented feature.
See also Provide the Viewer to some of your users.