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="2115" />
  </query-continue>
  <query>
    <pageswithprop>
      <page pageid="189" ns="0" title="Signal Identification Guide" value="Signal Identification Guide" />
      <page pageid="687" ns="2" title="User:Cartoonman" value="Cartoonman&#039;s Corner" />
      <page pageid="1060" ns="10" title="Template:DatabaseUNID" value="Unidentified Signals" />
      <page pageid="2108" ns="14" title="Category:Amateur Radio" value="Amateur Radio" />
      <page pageid="2109" ns="14" title="Category:Aviation" value="Aviation" />
      <page pageid="2110" ns="14" title="Category:Marine" value="Marine" />
      <page pageid="2111" ns="14" title="Category:Military" value="Military" />
      <page pageid="2112" ns="14" title="Category:HF" value="High Frequency (HF)" />
      <page pageid="2113" ns="14" title="Category:LF" value="Low Frequency (LF)" />
      <page pageid="2114" ns="14" title="Category:MF" value="Medium Frequency (MF)" />
    </pageswithprop>
  </query>
</api>