All web applications has CSS and JS files. But, now a days most of the developers wants to include only minified JS and CSS files. Because, normal JS and CSS files having unnecessary characters in source codes. These unnecessary characters usually include white space characters, new line characters, comments, and sometimes block delimiters. These are very important only for code readability, but not needed for execution process. These unnecessary characters increase file size and it will be affect performance too. For this reason, the minification (also minimisation or minimization) is very important. We have lot of JS and CSS minification online convertor and have lot of JAVA libraries available in internet. But, best one is, YUI Library ( Yahoo userInterface Library ). Because, it is very lightweight core library and also it is a free open source Library.