Hi I've got a parent div of 100% inside there is a child div with width size in px but when I make the browser smaller the parent div stop been 100% and becames smaller than the child div is there a way I can make the parent div to always be 100% of the browser

here my code
<style type="text/css">
#parent_div {background-color:red; width:100%; padding:10px;}
.child_div {background-color:yellow; width:884px; margin:auto; clear:both; padding:10px;}

<div id="parent_div">
	<div class="child_div">
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