<?xml version="1.0" encoding="UTF-8"?>
<root>
  <!-- Error 1: Correctly formed element -->
  <validElement id="1">Standard data</validElement>

  <!-- Error 2: Mismatched closing tag -->
  <userRecord>
    <username>jdoe88</username>
    <email>jdoe@example.com</address>
  </userRecord>

  <!-- Error 3: Unclosed tag at the end of a block -->
  <metadata>
    <version>1.2.0</version>
    <status>Active
  </metadata>

  <!-- Error 4: Undeclared namespace prefix 'h' -->
  <content>
    <h:table border="1">
      <h:tr>
        <h:td>Cell 1</h:td>
      </h:tr>
    </h:table>
  </content>

  <!-- Error 5: Attribute without quotes -->
  <settings theme=dark autoSave="true" />

  <!-- Error 6: Duplicate attributes -->
  <profile id="44" id="55">
    <bio>Software developer based in Seattle.</bio>
  </profile>

  <!-- Error 7: Illegal character in data -->
  <formula>If A < B and C > D then output result</formula>
</root>