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>
    <pageswithprop pwpcontinue="746" />
  </query-continue>
  <query>
    <pageswithprop>
      <page pageid="1" ns="0" title="Main Page" value="BioCore @ CRG" />
      <page pageid="11" ns="2" title="User:Thermoso" value="Toni Hermoso Pulido" />
      <page pageid="18" ns="100" title="Private:ChipSeq" value="ChIP-seq Procedure" />
      <page pageid="24" ns="100" title="Private:Projects" value="Projects of Bioinformatics Core Facility" />
      <page pageid="168" ns="2" title="User:Lcozzuto" value="Luca Cozzuto" />
      <page pageid="169" ns="2" title="User:Fmancuso" value="Francesco Mattia Mancuso" />
      <page pageid="700" ns="0" title="Lab Service Wiki: a wiki-based data management solution for laboratories production services" value="Lab Service Wiki: a wiki-based data management solution for laboratories production services" />
      <page pageid="701" ns="0" title="Extracting biological meaning from large gene list with DAVID" value="Extracting biological meaning from large gene list with DAVID" />
      <page pageid="704" ns="0" title="Semantic web technologies applied to bioinformatics and laboratory data management" value="Semantic web technologies applied to bioinformatics and laboratory data management" />
      <page pageid="715" ns="14" title="Category:Software" value="Software" />
    </pageswithprop>
  </query>
</api>