Pull Down Menu

The options in one of my pull down menus link to other sections of the same
page. I've noticed that selecting one of these links opens a new instance of
the entire page instead of just scrolling down to the appropriate section.
How can I make the menu do what I want?

<form name="f1">
<select name="s1" class="hnhjumpbox">
<option value="#">See our Policies...</option>
<option value="#">----------</option>
<option value="#service">Service</option>
<option value="#payment">Payment</option>
<option value="#packing">Packing</option>
<option value="#shipping">Shipping</option>
<option value="#returns">Returns</option>
</select>&nbsp;<input type="button" name="test" class="hnhjumpboxbutton"
value="Go" title="Select a link from the drop-down menu first!"
onClick="location=document.f1.s1.options[document.f1.s1.selectedIndex].value
;"></form>

For instance, I have an anchor at the Payment section. When I select the
Payment link from the pull down menu, a new instance of the page opens and
then jumps down to the Payment section. I want it to jump down to the
payment section without opening a new page.