Final answer:
Web developers used JavaScript to conduct inline validation in HTML forms prior to HTML5.
Step-by-step explanation:
Prior to HTML5, web developers used JavaScript to conduct inline validation in HTML forms.
Inline validation is the process of checking user input to ensure its correctness while the user is still filling out the form.
Developers would write custom JavaScript code that would run in the browser and perform validation checks on the form inputs. This code would be triggered by events like submitting the form or moving focus away from a particular input field.