Within the design of software development there are two design activities that affect the product: User Interface (UI) and the User Experience (UX), often these are bundled together and both completed by a single designer but they are two separate disciplines each of significant important.
The User Experience design is how people will interact with the product.
Examples of Bad UX include the following:
Where the requirements for a valid password are long or convoluted.
Or the above form which overcomplicates the act of donating by including far too many fields for the user to complete when all that is really required is a name and then the payment details.
Finally, there's an oft-quoted story of how a single button was causing Amazon to lose $300 million per year in revenue.
After choosing to purchase a product and then clicking checkout users were taken to a screen asking them to either login to an existing account or register a new one.
Without realising at the time this step frustrated a lot of users who only wanted to order the product, they had no need to keep an account with Amazon and believed Amazon only wanted them to register in order to collect their personal information.
The solution to this issue was to change the button from "register" to "continue" and suddenly users were no longer deterred.