CSS实现页面风格的选择
网上有很多如下的代码,可是确没有解释以下的代码的文章.而我自己尝试着这三个步骤,都不成功.我想问下各位,有没有人能指点一下.
在这个js里面,有两个window.onload函数.我想问下,一个文件里,是否允许两个window.onload.


1.   styleswitcher.js  
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);  


2、CSS调用：

CODE:  
<link   rel= "stylesheet "   type= "text/css "   href= "default.css "   />   //默认的样式这样调用
<link   rel= "stylesheet "   type= "text/css "