Consider the following minimal example (taken from this answer):
\documentclass{article}
\usepackage{color}
\usepackage{ulem}
\newcommand\hl{\bgroup\markoverwith
{\textcolor{yellow}{\rule[-.5ex]{2pt}{2.5ex}}}\ULon}
\begin{document}
This is a test \hl{Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.} text.
\end{document}
If you look at the output carefully, you will notice that color has covered small parts of some leters. How is this fixed?
Here is a screenshot of the output:



fis typeset afterfbut it covers the serif off. I have no idea how to solve the problem properly. – Leo Liu Jul 12 '15 at 06:05