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>
    <pages>
      <page pageid="29" ns="0" title="Pro cidr2mask and mask2cidr scripts" />
      <page pageid="59" ns="0" title="Gentoo kde xorg setup log" />
      <page pageid="137" ns="0" title="bash script parsing arguments with getopts" />
      <page pageid="170" ns="0" title="Samba - mounting share from linux" />
      <page pageid="327" ns="0" title="windows clients and cups" />
      <page pageid="354" ns="0" title="ssh-agent user setup" />
      <page pageid="612" ns="0" title="kvm" />
    </pages>
  </query>
</api>