This means that if you have to update your code, you only need to fix the central files and not every page that uses the code. If you need to add new functionality, you don't have to change any of your existing pages. You can include additional attributes to your tag that introduce new behaviors while retaining your old attributes and keeping all your old pages working. But later in the project, you want to choose the shade of blue. All of your old tags still work to produce blue text, but now you can use the same tag to produce blue text of any shade.
Tags promote code reuse.
Code that is used over time has been more thoroughly tested and will have fewer bugs. As a result, JSP pages that use custom tags will have fewer bugs and be easier to maintain. Tag libraries offer an easy way to reuse code. One of the standard ways to reuse code in a server-side language is to use templates. A tag library is a far better solution compared to a template library.