I have checked my end and it works fine. You can't use Javascript code inside the Raw HTML addon.
<form action="https://www.sandbox.paypal.com/donate/?hosted_button_id=Q48Z63DDHE2UE" method="post">
<!-- Identify your business so that you can collect the payments. -->
<input type="hidden" name="business" value="[email protected]">
<!-- Specify details about the contribution -->
<input type="hidden" name="no_recurring" value="0">
<input type="hidden" name="item_name" value="Friends of the Park">
<input type="hidden" name="item_number" value="Fall Cleanup Campaign">
<input type="hidden" name="amount" value="25.00">
<input type="hidden" name="currency_code" value="USD">
<!-- Display the payment button. -->
<input type="image" name="submit" src="https://www.paypalobjects.com/en_US/i/btn/btn_donate_LG.gif" alt="Donate">
<img alt="" width="1" height="1" src="https://www.paypalobjects.com/en_US/i/scr/pixel.gif" >
</form>
Or
<form action="https://www.sandbox.paypal.com/donate/?hosted_button_id=Q48Z63DDHE2UE" method="post" target="_top">
<input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_donateCC_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.sandbox.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>