How do I prevent <div> from overlapping on zoom?

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CSS

HTML

I am displaying three div's side by side, they look well at normal screen size but on zooming screen as the div shrinks text inside it also shrinks and images seem to be cut (size of image is being cut on further zoom). Bottom line I don't want content inside divs messed up on zooming, tried overflow: scroll for body but on zooming no scroll bar appears. I think scroll bar would help in keeping the content inside div safe.
jsfiddle

<div id='container' style='width:100%;'>
<div class='left' style='height:20px;width:21%;float:left;border:1px solid black;box-sizing: border-box;height:200px;'>
</div>
<div class='center' style='height:20px;width:56%;float:left;border:1px solid blue;box-sizing: border-box;height:200px;'>
</div>
<div class='right' style='height:20px;width:23%;float:right;border:1px solid red;box-sizing: border-box;height:200px;'>
</div>
</div>