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">

Note: Displaying PayPal logos in frames can also cause run-time errors for most browsers if the website uses JavaScript.