Blank Screen of Death

After trying to figure out how to customize Pro Sites for a custom button my website, all sub sites and the dashboards are white now.

What the last thing I did was to paste the following into the field for manual pay methods:

<form action="" method="post">
<input type="hidden" name="cmd" value="_xclick-subscriptions">
<input type="hidden" name="business" value="">
<input type="hidden" name="lc" value="de_DE">
<input type="hidden" name="item_name" value="Abo Button">
<input type="hidden" name="no_note" value="1">
<input type="hidden" name="no_shipping" value="2">
<input type="hidden" name="rm" value="1">
<input type="hidden" name="return" value="">
<input type="hidden" name="cancel_return" value="">
<input type="hidden" name="src" value="1"> <input type="hidden" name="a3" value="10.00">
<input type="hidden" name="p3" value="1">
<input type="hidden" name="t3" value="M">
<input type="hidden" name="currency_code" value="EUR">
<input type="hidden" name="bn" value="PP-SubscriptionsBF:btn_subscribeCC_LG.gif:NonHosted"> <input type="image" src="" border="0" name="submit" alt="Jetzt einfach, schnell und sicher online bezahlen – mit PayPal.">
<img alt="" border="0" src="" width="1" height="1"> </form>

I'm trying now to identify this data within mysql database to delete it with the hope that this was causing the issue.

Any help possible or ideas?