XML Parsing Error: mismatched tag. Expected

use Firefox Worthy of being a technical nerd , Even one HTML Label Department specification , Will give ERROR MESSAGE.
Long long ago Used to IE Development , since chrome After the birth of , Take your time chrome Drive away IE, Occasionally, Firefox.
Because I don't use it very often Firefox, During debugging , Code that does not affect the business is ignored , Use today Firefox debugging , Find the following tips ：

XML Parsing Error: mismatched tag. Expected: </img>.
Location: http://yourdomain.com/?v=0.3880621168625962
Line Number 449, Column 76:

Go to the wrong point and have a look , The original picture element tag lacks closing behavior

Before the change ：
<img src="animate.webp">

After modification ：
<img src="animate.webp" />

The above two are in HTML Both are feasible , But if you expect XML The software uses your code , The back is closed ( Oblique line “/”) Is a must .