With a LOT of help from everybody here I got it working.
For everybody that's interested here's the code:
Works in IE, FF and Opera

css:
code:
.spoiler{
color: #000000;
}
javascript:
code:
<script>
function hide(id){
document.getElementById(id).style.display = 'none';
}
function show(id){
document.getElementById(id).style.display = '';
}
function spoilerhide(){
for (i=0;i<document.getElementsByTagName('div').length;i++) {
if (document.getElementsByTagName('div')[i].className == 'spoiler') {
document.getElementsByTagName('div')[i].style.color = '#000000';
}
}
}
function spoilershow(){
for (i=0;i<document.getElementsByTagName('div').length;i++) {
if (document.getElementsByTagName('div')[i].className == 'spoiler') {
document.getElementsByTagName('div')[i].style.color = '#FFFFFF';
}
}
}
</script>
HTML:
code:
<div id="div1">
<input type="button" onClick="hide('div1'); show('div2'); spoilershow();" value="Show Spoilers">
</div>
<div id="div2" style="display:none;">
<input type="button" onClick="show('div1'); hide('div2'); spoilerhide();" value="Hide spoilers">
</div>
Thanks everybody who helped
