You have pledged to a project, and you have a strange $1 charge on your card from Pozible! What's going on? 

This is a charge that is made to verify your card. It ensures that the credit card number provided is associated with a valid, open account charged successfully when a project is successful. 

Braintree, our card merchant verifies credit cards by running either a $0 or $1 authorisation and then automatically voiding it. For most processors, Visa and MasterCard are initially tried with $0 authorisations. Because some card types (like AmEx and Discover) don’t consistently support $0 authorisations, they are only tried with $1 requests. Where a $1 authorisation returns a successful result, it is immediately followed up with an automatic void request to ensure that the transaction will disappear from the cardholder's statement as soon as possible. 

Some banks don't recognise void requests immediately. It's possible you will still see the pending charge, however the void should be processed quickly and rectified on your statement. If you are concerned, you should contact your bank for them to follow up for you. 

Read more here.