Fixit jQuery plugin can be used to fix the element at a certain position when the webpage is scrolled and the element is to be hidden, so that the element stay visible on the webpage.
In this tutorial you will find out how to create a sticky navigation bar that remains fixed to the top after scroll by using CSS and jQuery.
MakeFixed.js is a jQuery plugin to dynamically set up elements to be fixed during scroll. It's lightweight and allows callback functions.
ScrollFix is a jQuery plugin for making an element fixed when it goes out of view.