there are many ways to do it.
in your skin1/customer/main/product.tpl
find the lines
Code:
{if $product.taxed_price gt 0 && $product.list_price gt 0}
<div class="save" id="save_percent_box"{if $product.appearance.market_price_discount} style="display: none;"{/if}>
<span id="save_percent">{$product.appearance.market_price_discount}</span>%
</div>
{/if}
and remove it or change like this:
Code:
{* {if $product.taxed_price gt 0 && $product.list_price gt 0}
<div class="save" id="save_percent_box"{if $product.appearance.market_price_discount} style="display: none;"{/if}>
<span id="save_percent">{$product.appearance.market_price_discount}</span>%
</div>
{/if}*}
There is a bug in original template that caused showing this sign on product's description page only for products that has no discount
so you may change it to
Code:
{if $product.taxed_price gt 0 && $product.list_price gt 0}
<div class="save" id="save_percent_box"{if $product.appearance.market_price_discount eq 0} style="display: none;"{/if}>
<span id="save_percent">{$product.appearance.market_price_discount}</span>%
</div>
{/if}
to function properly