When you develop your website, you must make sure that all your users should see your website the way you intended it to be seen. This is the last but the essential step of any web build that you can't afford to get wrong.
So to help you along and make sure you don't get things wrong, here are the 10 main things you need to do to ensure that your site will work atleast on all major browsers.
01. Validate your code
Chances to experience wierd behaviour are more between browsers if the code is not strictly validated, so check it with https://validator.w3.org/ to make sure that you are following the standards.
02. Fail gracefully
Keep in your mind while desigining your site, that not all functionality will work. It's good to check how it renders without JS or CSS enabled, just to test if the user can atleast tell what is happening just based on content alone.
03. Know your audience
You have to make sure that you understand the trageted browsers and devices. If your page is mostly for mobile users or if you are working within a company where still legacy browsers are used. So you have to design and test accordingly.
04. Consider using a framework
05. Keep your design simple
It's pretty obvious that the less advanced CSS features you use, the fewer problems you will have in terms of cross browsers. Do give that multiple thoughts whether you really need them.
06. Reuse and reduce components
Managing your CSS sensibly, through to utilizing web segments to modularise your whole website. So you have to test and maintain similar changes in fewer places which is definitely easier to manage.
07. Test with the difficult browsers first
If you are already aware of the browsers you need to support, then start out with that. If you know you need to support safari, then test on Safari first. You don't want to waste most of your time in testing befpre actually discovering the first issue
08. Create test scripts
Even if you are working as a developer, you should even for simpler sites define the set of tests at your end that you expect to run in each browser. Otherwise, you will miss the things at the end.
09. Test as you go along
This is way important for something that you think might be tricky. Start testing along without waiting to finish developing. You have to take iterative approach if you want to catch issues early and save time.
10. Check your features
Before using new features, do check browser support for them and make use of feature detection and polyfills if you have to rely on something that is not being supported.