Final answer:
An online storefront developer should test the different versions of web browsers in order to ensure usability for all users.
Step-by-step explanation:
An online storefront developer should test the different versions of web browsers in order to ensure usability for all users. Web browsers are the software applications used to access online storefronts, and they can vary in terms of their capabilities and compatibility with different web technologies. By testing different versions of web browsers, developers can identify any issues or discrepancies that may affect the user experience and make necessary adjustments to optimize the storefront's compatibility.