<p>When the auxiliary verb of a compound form is <span style="font-style: italic;">avoir</span>, <strong>the past participle does not agree in number and gender</strong> with its subject. The only exception is when the direct object precedes the past participle</strong> in the sentence:</p>
<div class="conjugation_explanation_example_sentence">Voilà l'<span class="green_emphasis">erreur</span> que j'ai <span class="brown_emphasis">faite.</span> (<span style="font-style: italic;">This is the mistake I made.</span>)</div>
French conjugation explanation