client_is_running.js

// http://localhost:26843/client_is_running.js

function client_is_running() { return 1; }

is_hitbliss_running.js

function viewInHitBliss(uri) {
  if (typeof window.client_is_running === 'function' && client_is_running()) {
    window.location = uri;
  } else {
    window.location = '/download.html';
  }
}

view_in_hitbliss.html

<a href="javascript:viewInHitBliss('hitbliss:i=6734');" class="button large">View in HitBliss</a>