Three column CSS with liquid text in middle column how please?

Hello everyone, please help me correct this CSS. I have these HTML markup and CSS:
<div class="leftbox"> </div> <div class="middlebox"> sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text sample text samp ...