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body {background-color:red;}

第二個是背景為綠色的CSS文件（green.css）CSS中的內容為： 

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body {background-color:green;}

第三個是背景為黃色的CSS文件（yellow.css）CSS中的內容為：

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body {background-color:yellow;}

然后在xthml文件中加入這三個CSS的鏈接

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<link rel="alternate stylesheet" href="red.css" type="text/css" title="red" media="screen, projection"/>
<link rel="stylesheet" href="green.css" type="text/css" title="green" media="screen, projection"/>
<link rel="alternate stylesheet" href="yellow.css" type="text/css" title="yellow" media="screen, projection"/>

這三個中除了title不一樣外還有一個地方有所不同，那就是REL。第一個與第三個都是alternate stylesheet只有第二個是stylesheet。這第二個就是當然樣式。

在鏈接下面再導入一個JS文件，用來控制這個樣式切換

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function setActiveStyleSheet(title) {
  var i, a, main;
  if (title) {
  for(i=0; (a = document.getElementsByTagName('link')[i]); i++) {
  if(a.getAttribute('rel').indexOf('style') != -1 && a.getAttribute('title')) {
  a.disabled = true;
  if(a.getAttribute('title') == title) a.disabled = false;
  }
  }
  }
  }
  function getActiveStyleSheet() {
  var i, a;
  for(i=0; (a = document.getElementsByTagName('link')[i]); i++) {
  if(a.getAttribute('rel').indexOf('style') != -1 && a.getAttribute('title') && !a.disabled) return a.getAttribute('title');
  }
  return null;
}

在合適的地方加入三個切換按鈕

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<a href="javascript :void()" onclick="setActiveStyleSheet('red'); return false;" title="紅色樣式"></a>
<a href="javascript :void()" onclick="setActiveStyleSheet('green'); return false;" title="綠色樣式"></a>
<a href="javascript :void()" onclick="setActiveStyleSheet('yellow'); return false;" title="黃色樣式"></a>
<a href="javascript :void()" onclick="setActiveStyleSheet('none'); return false;" title="沒有樣式"></a>

好了發布試試點那三個切換鏈接！是不是已經切換了樣式？


補遺：帶有記憶功能的JS文檔

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function setActiveStyleSheet(title) {
var i, a, main;
for(i=0; (a = document.getElementsByTagName
("link")[i]); i++) {
if(a.getAttribute("rel").indexOf("style")
!= -1 && a.getAttribute("title")) {
a.disabled = true;
if(a.getAttribute("title") == title)
a.disabled = false;
}
}
}
function getActiveStyleSheet() {
var i, a;
for(i=0; (a = document.getElementsByTagName
("link")[i]); i++) {
if(a.getAttribute("rel").indexOf("style")
!= -1 && a.getAttribute("title") && !a.disabled)
return a.getAttribute("title");
}
return null;
}
function getPreferredStyleSheet() {
var i, a;
for(i=0; (a = document.getElementsByTagName
("link")[i]); i++) {
if(a.getAttribute("rel").indexOf("style") != -1
&& a.getAttribute("rel").indexOf("alt") == -1
&& a.getAttribute("title")
) return a.getAttribute("title");
}
return null;
}
function createCookie(name,value,days) {
if (days) {
var date = new Date();
date.setTime(date.getTime()+(days*24*60*60*1000));
var expires = "; expires="+date.toGMTString();
}
else expires = "";
document.cookie = name+"="+value+expires+";
path=/";
}
function readCookie(name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return
c.substring(nameEQ.length,c.length);
}
return null;
}
window.onload = function(e) {
var cookie = readCookie("style");
var title = cookie ? cookie :
getPreferredStyleSheet();
setActiveStyleSheet(title);
}
window.onunload = function(e) {
var title = getActiveStyleSheet();
createCookie("style", title, 365);
}
var cookie = readCookie("style");
var title = cookie ? cookie :
getPreferredStyleSheet();
setActiveStyleSheet(title);