Position Relative on Different Browsers and Responsive Design

I’ve noticed that “position relative” with a set position (e.g., top: 100px) changes on different browsers (especially doesn’t work on the soon to be defunct IE) and on different platforms (e.g., desktop vs. mobile). Is this a problem that can be fixed or might there be a problem with the way I’ve coded it. (Sorry, I don’t have the code right now–just something I remembered occurring.)

If i look at the documentation (link) it should work on most browsers (scroll down to see the browser compatibility), could you show some code?

I deleted it because it didn’t work on IE. I guess that won’t be a problem soon. I set position in from the left.