AndreyP,
The HTML that I try to use is the PayPal form button. Here is the code:

<form action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_xclick">
<input type="hidden" name="business" value="dfpenner@aol.com">
<input type="hidden" name="item_name" value="Test">
<input type="hidden" name="item_number" see more value="Tester">
<input type="hidden" name="amount" value="2.00">
<input type="hidden" name="no_shipping" value="0">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="currency_code" value="USD">
<input type="hidden" name="lc" value="US">
<input type="hidden" name="bn" value="PP-BuyNowBF">
<input type="image" src="https://www.paypal.com/en_US/i/btn/btn_buynow_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>

I'm thinking because it is within a form method is why it is getting stripped but don't know for sure.