We love answering GSAP-related questions, but in order to get you a fast, accurate answer it is very important that you provide code we can test.
Your problem may be related to CSS, HTML, a framework or JavaScript (or a mixture of those). A tiny code snippet (outside of its context), is difficult to diagnose. We need code that we can dig into and play with...quickly.
We are big fans of CodePen.io, an online editor that allows you to create (and share) demos that are easy