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>
    <backlinks blcontinue="0|Main_Page|1575" />
  </query-continue>
  <query>
    <backlinks>
      <bl pageid="3" ns="4" title="Hydrogenaudio Knowledgebase:Protection log" />
      <bl pageid="728" ns="0" title="Topic Index" />
      <bl pageid="729" ns="0" title="Hydrogenaudio" />
      <bl pageid="737" ns="5" title="Hydrogenaudio Knowledgebase talk:Main Page/Real talk" />
      <bl pageid="773" ns="5" title="Hydrogenaudio Knowledgebase talk:Wiki Policy" />
      <bl pageid="799" ns="1" title="Talk:Topic Index" />
      <bl pageid="863" ns="4" title="Hydrogenaudio Knowledgebase:Searching" />
      <bl pageid="870" ns="1" title="Talk:MP3" />
      <bl pageid="1115" ns="101" title="Foobar2000 Talk:Foobar2000" />
      <bl pageid="1215" ns="12" title="Help:Editing" />
    </backlinks>
  </query>
</api>