Hey guys, does anybody know how to prevent CMS to overwrite changes in content?

I have content with some advanced HTML tags. FOr some reason CMS removing all div and other tags and leaves only small number of sections intact. Is there a settings somewhere to prevent CMS from interfiring with content?

Example like that:

<div class="relnw"><div class="relnt"><div class="relnb">
        <div class="inner">
            <h2>Related Links:</h2>
            <div class="awrap">
                <a href="../campus-EMEA-analyst-associate-internships.aspx" title="Europe, Middle East and Africa analyst & associate internships &raquo;" style="letter-spacing: -0.1px;">
                <b>Europe, Middle East and Africa analyst & associate internships&nbsp;&raquo;</b></a>
            </div>
        </div>
    </div>
</div>
</div>

after I save/publish article with this insert as HTML that is what it looks like:

<div class="relnw">
            <h2>Related Links:</h2>
            <div class="awrap">
                <a href="../campus-EMEA-analyst-associate-internships.aspx" title="Europe, Middle East and Africa analyst & associate internships &raquo;" style="letter-spacing: -0.1px;">
                <b>Europe, Middle East and Africa analyst & associate internships&nbsp;&raquo;</b></a>
            </div>
        </div>