Same Css showing different on different website?

Question

I am injecting a sidebar with it's css from the chrome extension to different website. But the result is, the sidebar is a little different when injected on different websites?

Answer 1

https://caniuse.com before writing some css code check here is it supported in all browsers or not because some properties are not supported by all browsers that's why.

Answer 2

I am using the same browser to inject different websites.. but every website is showing a little different result