Styling HTML Form Validation Error Messages with CSS: A Current Limitation
While HTML form validation provides valuable functionality, customizing the appearance of its error messages with CSS remains a challenge. Currently, there is no direct way to modify the styling of the tooltips that display these errors.
Alternate Solution
One alternative is to disable browser validation and implement your own client-side validation scripts. This approach allows you to fully control the design and display of error messages.
Disabling Browser Validation
As mentioned in the article referenced (https://blog.oldworld.fr/index.php?post/2010/11/17/HTML5-Forms-Validation-in-Firefox-4), you can opt out of browser validation by adding the novalidate attribute to the