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>
    <alltransclusions gatcontinue="Documentation|278" />
  </query-continue>
  <query>
    <pages>
      <page pageid="263" ns="10" title="الگو:Infobox software" />
      <page pageid="265" ns="10" title="الگو:-" />
      <page pageid="269" ns="10" title="الگو:Documentation subpage" />
      <page pageid="270" ns="10" title="الگو:Fmbox" />
      <page pageid="271" ns="10" title="الگو:Infobox" />
      <page pageid="274" ns="10" title="الگو:Lts" />
      <page pageid="275" ns="10" title="الگو:MONTHNAME" />
      <page pageid="276" ns="10" title="الگو:MONTHNUMBER" />
      <page pageid="322" ns="0" title="Mac OS X Tiger" />
      <page pageid="352" ns="0" title="Essential Tips" />
    </pages>
  </query>
</api>