How to perform cross browser check

Question

How to make your website cross browser compatible?

Answer 1

The first thing you should do is make your website HTML5 compliant. You can verify this using tools like:
https://validator.w3.org/
If mobile browsers are part of your concern, the next step is a bit of mobile browser testing. This could be as simple as running your site through a few happy path scenarios at a very narrow width to simulate a mobile browser. The desktop browser's developer tools could have features to simulate different mobile devices too.
JavaScript is much harder to automatically validate or test. You can transpile to old ECMAScript. This processing of code can reveal some syntax errors and help you run in old browsers.
JavaScript can often use features that aren't standard or are compatible with only some web browsers. Even if you have some automated tests, you'll need to manually test in multiple browsers too.
Check the following for tips on testing in multiple browsers:
https://developer.mozilla.org/en-US/docs/Learn/Tools_and_testing/Cross_browser_testing/Introduction