<select name="guide_select" id="guide_select" style="width: 200px;font-family: verdana; font-size: 12px;" onchange="
for (i=1; i<=6; i++)
if (this.options[this.selectedIndex].value==i)
show_layers('s'+i);
else hide_layers('s'+i);">
<option value="1">.....</option>
.....
<option value="6">.....</option>
</select>

function show_layers(id)
{
document.getElementById(id).style.display='block';
}

function hide_layers(id)
{
document.getElementById(id).style.display='none';
}

<script type="text/javascript">
function show_guide (s){
for (i=1; i<=6; i++)
if (s==i)
show_layers('s'+i);
else hide_layers('s'+i);
}
function show_layers(id)
{
document.getElementById(id).style.display='block';
}

function hide_layers(id)
{
document.getElementById(id).style.display='none';
}
</script>

<select name="guide_select" id="guide_select" style="width: 200px;font-family: verdana; font-size: 12px;" onchange="show_guide(this.options[this.selectedIndex].value);">