.mediumtextwhite {
	font-family: "Times New Roman", Times, serif;
	font-size: 30px;
	font-style: normal;
	font-weight: normal;
	color: #FFF;
	text-align: center;
}
<form target="paypal" action="https://www.paypal.com/cgi-bin/webscr" method="post">
  <input type="hidden" name="cmd" value="_cart">
  <input type="hidden" name="business" value="MP4Z9MLCVNE7Q">
  <input type="hidden" name="lc" value="US">
  <input type="hidden" name="item_name" value="Shiroi Neko">
  <input type="hidden" name="item_number" value="S 062">
  <input type="hidden" name="button_subtype" value="products">
  <input type="hidden" name="cn" value="Add special instructions to the seller">
  <input type="hidden" name="no_shipping" value="2">
  <input type="hidden" name="rm" value="1">
  <input type="hidden" name="return" value="http://www.shiroinekoonline.com/thankyou.html">
  <input type="hidden" name="cancel_return" value="http://www.shiroinekoonline.com/catalogue.html">
  <input type="hidden" name="currency_code" value="USD">
  <input type="hidden" name="tax_rate" value="0.000">
  <input type="hidden" name="shipping" value="5.00">
  <input type="hidden" name="add" value="1">
  <input type="hidden" name="bn" value="PP-ShopCartBF:btn_cart_LG.gif:NonHosted">
  <table>
  <tr><td><input type="hidden" name="on0" value="SIZES">SIZES</td></tr><tr><td><select name="os0">
    <option value="Size. M">Size. M $25.00</option>
    <option value="Size. L">Size. L $25.00</option>
  </select> </td></tr>
  </table>
  <input type="hidden" name="currency_code" value="USD">
  <input type="hidden" name="option_select0" value="Size. M">
  <input type="hidden" name="option_amount0" value="25.00">
  <input type="hidden" name="option_select1" value="Size. L">
  <input type="hidden" name="option_amount1" value="25.00">
  <input type="hidden" name="option_index" value="0">
  <input type="image" src="https://www.paypal.com/en_US/i/btn/btn_cart_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>