Javascript: Check if user do changes on Code Snippet
<p>is there a javascript method to check if a user changes a given code?
Example:</p>

<pre><code>&lt;div id="mycodestyle"&gt;
&lt;a href="http://www.example.com"&gt;&lt;img src="image.gif"&gt;&lt;/a&gt;
&lt;/div&gt;
</code></pre>

<p>if the user now changes the code like</p>

<pre><code>&lt;div id="mycodestyle"&gt;
&lt;img src="image.gif"&gt;
&lt;/div&gt;
</code></pre>

<p>he get's a message -> Code modified. Extremetracking uses the same method, but I don´t know how they do it.
Here is the code of extremetracking</p>

<pre><code>&lt;div id="eXTReMe"&gt;
&lt;a href="http://extremetracking.com/open?login=example"&gt;

&lt;img src="http://t1.extreme-dm.com/i.gif" style="border: 0;"
height="38" width="41" id="EXim" alt="eXTReMe Tracker" /&gt;&lt;/a&gt;
&lt;script type="text/javascript"&gt;&lt;!--
EXref="";
top.document.referrer?EXref=top.document.referrer:EXref=document.referrer;
//--&gt;&lt;/script&gt;
&lt;script type="text/javascript"&gt;&lt;!--
var EXlogin='example' // Login
var EXvsrv='s10' // VServer
EXs=screen;
EXw=EXs.width;
navigator.appName!="Netscape"?EXb=EXs.colorDepth:EXb=EXs.pixelDepth;
EXsrc="src";
navigator.javaEnabled()==1?EXjv="y":EXjv="n";
EXd=document;
EXw?"":EXw="na";
EXb?"":EXb="na";
EXref?EXref=EXref:EXref=EXd.referrer;
EXd.write("&lt;img "+EXsrc+"=http://e1.extreme-dm.com",
"/"+EXvsrv+".g?login="+EXlogin+"&amp;amp;",
"jv="+EXjv+"&amp;amp;j=y&amp;amp;srw="+EXw+"&amp;amp;srb="+EXb+"&amp;amp;",
"l="+escape(EXref)+" height=1 width=1&gt;");
//--&gt;&lt;/script&gt;
&lt;noscript&gt;&lt;div id="neXTReMe"&gt;&lt;img height="1" width="1" alt=""
src="http://e1.extreme-dm.com/s10.g?login=example&amp;amp;j=n&amp;amp;jv=n" /&gt;
&lt;/div&gt;&lt;/noscript&gt;

&lt;/div&gt;
</code></pre>
