Image Changes when Page Refresh

Basically I have two images and when someone refreshes my page I want it to change the only thing is Im not sure whether this is the right code and if so were would it go.

Ok Here are my two codes one is the code I have found and the other is what is in my sidebar.

Sidebar.php Code

<div class="span-8 last">



<br>
<a href="http://www.talkthereds.net/forums">
<input type="image" src="<?php bloginfo('template_directory'); ?>/images/forumbutton.png" alt="Forums" title= Enter Forums!" />
   <br>
<br>
   <a href="http://www.talkthereds.net/forums">
<input type="image" src="<?php bloginfo('template_directory'); ?>/images/stevengerrard.png" alt="Profiles" title= Players Profiles" />
   <br>
<br>
<a href="http://www.talkthereds.net/wallpaper/">
<input type="image" src="<?php bloginfo('template_directory'); ?>/images/wallpapers.png" alt="Wallpaper" title= Wallpapers" />

   <br>
<br>
<div class="facebookbox">
		<script type="text/javascript" src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_GB"></script><script type="text/javascript">FB.init("7faf22262fbb62c398295cd8d6e78393");</script><fb:fan profile_id="74024673413" stream="0" connections="12" logobar="0" height="320" width="245";> </fb:fan>
           <div style="font-size:8px;"><a href="http://www.facebook.com/pages/Liverpool/Talktheredsnet/74024673413"></a></div>

		</div>


<div class="sidebar">



       <?php if(get_theme_option('socialnetworks') != '') {
		?>
   			<div class="addthis_toolbox">   
   			    <div class="custom_images">

   			    </div>
   			    <script type="text/javascript" src="http://s7.addthis.com/js/250/addthis_widget.js?pub=xa-4a65e1d93cd75e94"></script>
   			</div>
   			<?php
   		}
   	?>

	<?php if(get_theme_option('ads_125') != '') {
		?>




	<?php } ?>

	<?php if(get_theme_option('video') != '') {
		?>

	<?php
	}
	?>
	<ul>
		<?php 
				if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar() ) : ?>



		<?php endif; ?>
	</ul>
	<?php if(get_theme_option('ad_sidebar1_bottom') != '') {
	?>

	<?php
	}
	?>
</div>
</div>

JavaScript for the two Images

<script language="JavaScipt">

<!-- Begin
3rnd.today=new Date();
4rnd.seed=rnd.today.getTime();
5function rnd() {
6 rnd.seed = (rnd.seed*9301+49297) % 233280;
7 return rnd.seed/(233280.0);
8};
9
10function rand(number) {
11 var result = Math.ceil(rnd()*number);
12 if (!result)result++;
13 return result
14};
15
16var ad_cnt1 = 2;
17var ad1 = rand (ad_cnt1);
18var link1;
19var adBanner1;
20var width1
21var height1
22if (ad1==1) {
23link1="YOUR LINK HERE";
24adBanner1="IMAGE1.jpg";
25width1="304";
26height1="130"
27alt1="YOUR IMAGE NAME";
28}
29if (ad1==2) {
30link1="YOUR LINK HERE";
31adBanner1="IMAGE1.jpg";
32width1="304";
33height1="130";
34alt1="YOUR IMAGE NAME";
35}
36document.write('<a href="' + link1 + '" target="_top">');
37document.write('<img src="' + adBanner1 + '" width=' + width1 + ' height=' + height1 + ' border=0 alt="' + alt1 + '"></a>');
38document.write('');
39// End --> 

</scipt>