help with spoiler bbcode i'm trying to make

[tipoboy]

ok i had on my forum a spoiler bbcode, but i thought it would look better if it had an image instead of a text button to reveal the hidden text/image.

the bbcode for the original spoiler was:

<div class="spoiler"><script>
function showHide(what){
a=what.getElementsByTagName("div")[0];
if(a.style.display=='none'){
a.style.display='block';
}else{
a.style.display='none';
}}
</script>
<input type="button" onclick="showHide(this.parentNode)" value="Warning; Click to view spoiler"><b>( Click to show/hide )</b><div style="display:none">{param}</div></div>

so i changed the input type to image and added the path correctly and everything shows, that is until you click the image to reveal the hidden text/image.

it will reveal what i want but its also linking it to inline moderation so when you click it the text/image reveals the a second later your forwarded to the inline.php page.

Can someone help me with this, this is the code i am using for the image spoiler bbcode

<div class="spoiler">
<script>
function showHide(what){
a=what.getElementsByTagName("div")[0];
if(a.style.display=='none'){
a.style.display='block';
}else{
a.style.display='none';
}}
</script>
<input type="image"  onclick="showHide(this.parentNode)" src="images/misc/splr1.gif" width="50" height="50" border="0"><b>( Click to show/hide )</b><div style="display:none">{param}</div></div>

any help is greatfully appreciated