Need help for text in Text Modul

sorry, haven´t found this in the forum. The problem is:
I choose in Impreza the Text-Modul. There I insert text, but not in “visuell” but in “html” modus.

<div style="width: 300px; min-height: 280px;" id="c24pp-rent......<script>...erjwrjwrjl....</script> <p>Each time I insert this the page is doing fine, but as soon as I change one more thing anywhere in this post or page, the theme is destroying this code, even I don´t touch this “text-modul”.</p> <p>Who has a solution for me to solve this problem.<br> Thanks so much.<br> Bye<br> Klaus</p>