css实现右侧固定宽度，左侧宽度自适应_html/css_WEB-ITnose
反过来也可以：左侧宽度固定，右侧自适应。不管是左是右，反正就是一边宽度固定，一边宽度自适应。
这种布局比较常见，博客园很多默认主题就是这种。一般情况下，这种布局中宽度固定的区域是侧边栏，而自适应的区域是主体内容区??相信把侧边栏搞成自适应的人很少吧？
要实现这种布局，也算比较简单。我们先给出html结构：
<div id="wrap"> <div id="sidebar" style="height:240px;">固定宽度区</div> <div id="content" style="height:340px;">自适应区</div></div><div id="footer">后面的一个DIV，以确保前面的定位不会导致后面的变形</div>
代码中的#wrap的div，是用来包裹我们要定位的这两个区的；他后面还有个#footer，用来测试在前面的定位搞定后会不会导致后面的div错位??如果错位了，那证明我们的定位方法必须改进。
下面列举几个常见的方法：
1，固定宽度区浮动，自适应区不设宽度而设置 margin
我们拿右边定宽左边自适应来做示范,CSS代码如下：
#wrap { overflow: hidden; *zoom: 1; } #content ,#sidebar { background-color: #eee; } #sidebar { float: right; width: 300px; } #content { margin-right: 310px; } #footer {background-color: #f00;color:#fff; margin-top: 1em}其中，sidebar让他浮动，并设置了一个宽度；而content没有设置宽度。
大家要注意html中必须使用div标签，不要妄图使用什么p标签来达到目的。因为div有个默认属性，即如果不设置宽度，那他会自动填满他的父标签的宽度。这里的content就是例子。
当然我们不能让他填满了，填满了他就不能和sidebar保持同一行了。我们给他设置一个margin。由于sidebar在右边，所以我们设置content的margin-right值，值比sidebar的宽度大一点点??以便区分他们的范围。例子中是310.
假设content的默认宽度是100%，那么他设置了margin后，他的宽度就变成了100%-310，此时content发现自己的宽度可以与sidebar挤在同一行了，于是他就上来了。
而宽度100%是相对于他的父标签来的，如果我们改变了他父标签的宽度，那content的宽度也就会变??比如我们把浏览器窗口缩小，那wrap的宽度就会变小，而content的宽度也就变小??但，他的实际宽度100%-310始终是不会变的。
这个方法看起来很完美，只要我们记得清除浮动(这里我用了最简单的方法)，那footer也不会错位。而且无论content和sidebar谁更长，都不会对布局造成影响.
但实际上这个方法有个很老火的限制??html中sidebar必须在content之前！
但我需要sidebar在content之后！因为我的content里面才是网页的主要内容，我不想主要内容反而排在次要内容后面。
但如果sidebar在content之后，那上面的一切都会化为泡影。
2，标准浏览器的方法
当然，以不折腾人为标准的w3c标准早就为我们提供了制作这种自适应宽度的标准方法。那就简单了：把wrap设为display:table并指定宽度100%,然后把content+sidebar设为display:table-cell;然后只给sidebar指定一个宽度，那么content的宽度就变成自适应了。
代码很少，而且不会有额外标签。不过这是IE7都无效的方法。
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