Why did I get the error "PayPal cannot process this transaction because of a problem with the seller's website"?

The information contained in your PayPal button request contained unsupported special characters or high-ASCII characters.

If you use your button form fields to pass high-ASCII characters to PayPal, you need to include a "charset" form variable that identifies the character encoding. This ensures that we read your data correctly and that responses returned to you have the same encoding. You can pass the CHARSET programmatically or set it in your account.

Here's how to set the CHARSET in your account:

1. Click Account Settings above Log out.
2. Select Website payments under Products & Services.
3. Click Update next to PayPal button language encoding. 
4. Click More Options.
5. Under Encoding, select the encoding you wish to use. We suggest UTF-8.
6. Click Save.