How to prevent div-resize by user

[TIS]

I've just placed the code in a HTML-page build with divs:

<!-- #BeginSnippet name="CMS" -->
<div id="main" class="flexcroll">
<h1>Donec quis quamn...</h1>
Donec porttitor justo eget orci aliquet vitae pharetra massa molestie. Nullam varius nulla a ante laoreet scelerisque. Curabitur iaculis metus eu enim imperdiet eleifend. Donec quis quam eu nunc pharetra bibendum.
<br>
</div>
<!-- #EndSnippet -->

When opening the edit screen there is a possibility to resize the div-container, this is not what I intend to. It's shown in the attached graphic, near 3 the arrows ("<=="). Is there a way to prevent this?