Why did I get a URL Masking/Framing "timing out" error during checkout?
You got a timing error during checkout.
Displaying a payment page in a frame often results in errors because of problems connecting to PayPal's processing server.
According to the PayPal User Agreement, you can't use a PayPal logo to display a PayPal payment page of any kind inside a framed page. When PayPal logos are used in a frame, the PayPal URL (https://www.paypal.com/) doesn't appear in the address bar, nor is the security lock displayed. PayPal customers should never enter their PayPal account password into any page with a URL that doesn't begin with "https://www.paypal.com". If you use frames, look for the following line in your button code:
<form method="post" action="https://www.paypal.com/cgi-bin/webscr">
To prevent the PayPal payment page from appearing in a frame, add
target="paypal" so the HTML code looks like the following line:
<form method="post" action="https://www.paypal.com/cgi-bin/webscr" target="paypal">