You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information.
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="DMS_OH_O2.png|392" />
  </query-continue>
  <query>
    <pages>
      <page pageid="170" ns="0" title="Wet deposition" />
      <page pageid="389" ns="0" title="GEOS-Chem v9-01-02 benchmark history" />
      <page pageid="392" ns="0" title="Updating standard chemistry with JPL 10-6" />
      <page pageid="518" ns="0" title="Leaf area indices in GEOS-Chem" />
      <page pageid="634" ns="0" title="EMEP European anthropogenic emissions" />
      <page pageid="1894" ns="0" title="Advanced Git usage" />
    </pages>
  </query>
</api>