html - Why isn't my accessibility tool of enlarging text size working? -

i'm adding accessibility tool of users being able increase font-size of text on page, , being able go default font-size if wanted to. have made second css file holds css rules text increase. when click on icons made text larger/text smaller not work. can understand why? help.

html code on home page:

<div id="font-size-buttons">    <a href="#" onclick="changecss('notaccessible.css', 2);"><img src="http://www.me14ch.leedsnewmedia.net/slate/images2/fontmin.png" width="25" height"25" alt="switch original text size , colours"></a>   <a href="#" onclick="changecss('stylesheet.css', 2);"><img src="http://www.me14ch.leedsnewmedia.net/slate/images2/fontmax.png" width="30" height="30" alt="switch larger text , improved colour contrast"></a>   </div> 

some of default css stylesheet code:

.body { height: 100%; overflow: auto; padding-bottom: 25px; font-size: 0.75em;  } /* accessibility */  #font-size-buttons {     float: right;     clear: both;     margin-right: 5px;  } 

and css alternative stylesheet:

body {     font-size: 1.5em;  } 

and linking stylesheet code @ top of index.html page:

    <link href="stylesheet.css" rel="stylesheet" type="text/css" /> <link href="http://me14ch.leedsnewmedia.net/slate/notaccessible.css" rel=alternate stylesheet" type="text/css" title="access"/> 

the website link: www.me14ch.leedsnewmedia.net/slate

that's because changecss not defined.

in onclick="...."> execute piece of javascript, in case function called changecss variables 'notaccessible.css' , 2.

but in code have function called changecss. either have write function, or change html.

[edit]

made little example fiddle