Try this...
Code:
{if $products[product].avail ne 0}
{if $product.forsale ne "B"} {include file="buttons/add_to_cart.tpl" style="button" href="javascript:if (FormValidation()) document.orderform.submit()"}
{/if}
{else} [img]{$ImagesDir}/outofstock.gif[/img] {/if}