If you are new to modding, you know there is nothing more frustrating than entering in a bunch of code only to discover that you have made an XML error. And if you enter in a lot of code at once, locating the error can be a huge time sink, like finding the needle in the proverbial haystack. Frequently occurring errors like a missing ">" or "/" or a simple misspelling can be extremely difficult to detect just by eyeballing the relevant files. Fortunately, there is a way to speed the process up so that you don't have to spend your time searching for typos.
This is why it is extremely helpful to know about this kind of website:
If you have a simple typo or error, then all you need to do is load the xml file into the validator. It will tell you exactly where the problem is and what you need to fix. You can then simply copy and paste that line of code into the "find" function, and within seconds you will know exactly where the problem is and how to fix it.
I only discovered this online resource recently, but this is a must-have, especially if you code using such primitive tools as note pad, and can be a huge time saver.