XML Self Check?

[Christopher Johns]

is there an option to “check” an XML for errors? I’ve been modifying an XML per instructions.
Yet the program sees the new modifications to the file. I reopen the xml and all the info is intact. It seems like a real straight forward process, (I am a computer illiterate), editing the xml.
But still it fights me. So, this is why I am asking about a an Error Checker. Thank you all
PS. if I delete the new info that I added, the program works fine.

[Ekopalypse]

There is a plugin called XML Tools which can be used to
check the syntax of an xml file and, if you are having a schema file for your
xml file, you can check if the xml data itself is valid.