css,html_chrome环境，当窗口小于固定宽度层（p）时，怎么让背景层（.head）撑开？，css,html

chrome环境，当窗口小于固定宽度层（p）时，怎么让背景层（.head）撑开？

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style type="text/css">
        .head{
             height: 87px;
            background: #ccc;
        }

        .head p{
        margin:0 auto;
        display:block;
        width: 500px;
        }
    </style>
</head>
<body>
    <div class="head"><p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod
    tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam,
    quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo
    consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse
    cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
    proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p></div>
</body>
</html>

width: 500px;

->
min-width: 500px;

给.head

设置一个最小宽度

或者用js，当resize的时候设置head.width(window.width());


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