We've just released support for a useful little feature in PayPal's Pro gateway ("PayPal Website Payments Pro") which allows you to keep PayPal's payment page within the iframe on your website. This provides for a smoother experience for the guest, everything can take place within your website (even though the actual card details are still entered by the guest directly onto PayPal's servers), rather than having the payment stage take place on a new page altogether.
If you have a PayPal Website Payments Pro account, check the box "Keep payment page within iframe" under Settings > Online Bookings > Require payment with booking:
Then your guests will see a compact payment page, which will stay within the widget iframe, like this:
(This only works with PayPal Website Payments Pro, not Website Payments Standard. With Standard, the
guest is always sent out of your website to a whole new page to enter their card details).