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>
    <allimages gaicontinue="CONV_H2O2.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="411" ns="6" title="File:ACTA OH.png" />
      <page pageid="403" ns="6" title="File:ALD2 OH.png" />
      <page pageid="848" ns="6" title="File:ALD2 photolysis.png" />
      <page pageid="1907" ns="6" title="File:AOD compare July revised default.png" />
      <page pageid="1274" ns="6" title="File:BNU LAI 2010.png" />
      <page pageid="2265" ns="6" title="File:Benchmark Timers gcc-14.3.1 vs gcc-14.4.0.txt" />
      <page pageid="2266" ns="6" title="File:Benchmark Timers gchp-14.3.1 vs gchp-14.4.0.txt" />
      <page pageid="1122" ns="6" title="File:Boxes removed from EMEP mask.png" />
      <page pageid="454" ns="6" title="File:C2H6 0-8km TAO&amp;GC 2006.pdf" />
      <page pageid="404" ns="6" title="File:C2H6 OH.png" />
    </pages>
  </query>
</api>