<form data to thread breaks layout?

[doa24uk]

Hi guys,

I'm trying to add the following code to a thread (in a forum with HTML enabled for admins)

<form action="https://checkout.google.com/api/checkout/v2/checkoutForm/Merchant/xxxxxxxxxx" id="BB_BuyButtonForm" method="post" name="BB_BuyButtonForm">
    <input name="item_name_1" type="hidden" value="Assigned Value"/>
    <input name="item_description_1" type="hidden" value="Assigned Value"/>
    <input name="item_quantity_1" type="hidden" value="1"/>
    <input name="item_price_1" type="hidden" value="00.0"/>
    <input name="item_currency_1" type="hidden" value="GBP"/>
    <input name="shopping-cart.items.item-1.digital-content.url" type="hidden" value="http://myurl.com"/>
    <input name="_charset_" type="hidden" value="utf-8"/>
    <input alt="" src="https://checkout.google.com/buttons/buy.gif?merchant_id=xxxxxxxxxxx&amp;w=117&amp;h=48&amp;style=trans&amp;variant=text&amp;loc=en_US" type="image"/>
</form>

However it's breaking the layout (when it decides to show the graphic, otherwise it's blank)

Can anyone help with how to get this displaying correctly??

Thanks in advance.

DoA