常常設計頁面時用到三層DIV,頭DIV與腳DIV通常固定高度,而中間層DIV根據內容的多少,高度不定,咱們常常但願但內容不多時,腳DIV保持在底部,當內容不少時,腳DIV被中間內容擠到下面,但仍然始終保持在底部。javascript
position有四個參數:static | relative | absolute | fixedcss
position:static,意味元素沒有被定位,元素會出如今文檔本該出現位置,是頁面元素默認的定位的方式,通常無需指定,除非想要覆蓋以前設置的定位。html
position:relative,很明白,相對元素本該位置的偏移量 java
#nav{ position:relative; top:15px; left:20px; }
position:absolute,這時候元素已經脫離了文檔,文檔中已經沒有本身的本該的位置了,但咱們能夠經過left、bottom、left和right來規定其在文檔中位置。瀏覽器
#nav{ postion:absolute; botton:0px; }
咱們知道萬物都是相對的,元素進行上面設置了後就保證nav元素始終保持在底部了呢?nav元素離botton爲0px,是哪一個爲參照物呢,是父級元素還仍是瀏覽器呢,其實這裏分爲兩種狀況:post
若是父級元素(父級元素的父級、父級的父級的父級......)設置postion時,則子元素此時相對的是父級的,因此當內容過多時,腳DIV不能被擠到底部去。ui
若是父級元素(父級元素的父級、父級的父級的父級......)沒有設置postion時,則子元素此時相對的是瀏覽器的,因此當內容過少時,腳DIV不能被擠到底部去。url
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} function indexFunc(){ window.document.getElementById("about").style.display="none"; } </script> </head> <body> <div id="header"> <h1 class="blogtitle"> <a href="http://www.cnblogs.com/chenyuming507950417/">泥塘·物語</a> </h1> <p class="desc">滲透那青春年華的,是那些文字……</p> </div> <div id="ddnav"> <div id="nav"> <ul class="nav"> <li><a href="#" onclick="indexFunc();">主頁</a></li> </ul> <ul class="nav"> <li><a href="#" onclick="aboutFunc();">關於</a></li> </ul> </div> </div> <div id="top"> </div> <div class="content"> <div id="post-e0a6ac53-c204-4919-9fda-2021397c40b8"> <p><p class="MsoNormal" style="margin-bottom: 7.5pt; text-align: center; mso-pagination: widow-orphan;" align="center"> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">麥子,你是怎樣長進個人眼睛</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span> </strong><strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你站立的土地一直站着個人雙腳</span> </strong><strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">咱們同根而生,是夥伴</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">只是我比你在泥土上住得更久</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">我一生是生活的奴隸,爲了生計</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">一年一次,我用鋒利的鐮刀收割</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你的麥芒對着天,從沒刺傷我</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">爲讓我拿鐮的手有更多的力氣</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你在一盤磨裏走很長的路</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">把本身碾的粉身碎骨</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">我是在飢餓時學會了感恩</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">端起一碗飯就想你熟了的膚色</span> </strong><strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">想起在泥土上來回行走的季節</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">麥子,你年年回來吧,我年年愛你</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"></span></strong> </p></p> </div> <div id="about" style="display:none;"> <p><p class="MsoNormal" style="margin-bottom: 7.5pt; text-align: center; mso-pagination: widow-orphan;" align="center"> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">麥子,你是怎樣長進個人眼睛</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span> </strong><strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你站立的土地一直站着個人雙腳</span> </strong><strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">咱們同根而生,是夥伴</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">只是我比你在泥土上住得更久</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">我一生是生活的奴隸,爲了生計</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">一年一次,我用鋒利的鐮刀收割</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你的麥芒對着天,從沒刺傷我</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">爲讓我拿鐮的手有更多的力氣</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">你在一盤磨裏走很長的路</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">把本身碾的粉身碎骨</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">我是在飢餓時學會了感恩</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">端起一碗飯就想你熟了的膚色</span> </strong><strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">想起在泥土上來回行走的季節</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"><br /> </span></strong> <strong><span style="font-size: 14pt; font-family: 宋體;" lang="ZH">麥子,你年年回來吧,我年年愛你</span></strong> <strong><span style="font-size: 14pt; font-family: Arial;" lang="EN-US"></span></strong> </p></p> </div> </div> <div id="footer"> </div> <div id="footerbox"> <div class="footer"> <a href="http://lovecjh.com/">泥塘·物語</a> 滲透那青春年華的,是那些文字…… © Copyright 2017 </div> </div> <body> </html>
(1)http://blog.davidqiu.com/post/2013-06-17/40051753968spa
(2)http://www.cnblogs.com/ahjesus/archive/2011/11/26/2263986.html設計