How can I serve js and css from Drupal 7
You'll need a custom module for this (see the Module Developer's Guide if you're not already familiar with creating modules, it's pretty straightforward).

Once you've got your custom module set up you need to implement hook_menu() and define a callback function for your URL:

function MYMODULE_menu() {
  $items['globalmenu.html'] = array(
    'title' =&gt; 'Global Menu',
    'access callback' =&gt; TRUE, // If you want any source to be able to access this page
    'page callback' =&gt; 'MYMODULE_deliver_global_menu'
  ); 

  return $items;
}

function MYMODULE_deliver_global_menu() {
  print '&lt;div class="nav"&gt;...';
  drupal_exit();
}


Since Drupal will only actually apply the theme wrappers to a page if something is returned from the page callback, simply printing your HTML and calling drupal_exit() is all you need to do.

Sorry if some of that is stuff you already know, I thought it best to err on the side of caution.