You usually use the slash / (in HTML I mean) when you have to close a particular tag:
<p align="center"> text </p>
In this case your code is wrong because you didn’t use the slash in the correct way. Look here an example
<img src="https://stackoverflow.com/questions/16315688/image.gif" onerror="alert('Error')">
Also, /asimpletest/ is useless. Remove it.
solved What’s the meaning of the slash in the HTML tag? [closed]