I think the issue may have occurred because your row widget template had a <tr> element as it's root, which I believe is not valid html. If you want to have your row widget in a separate file, you could try making a RowWidget.html file with a full table in it and reference the row the same way your are doing now: @Templated("RowWidget.html#mediaRow")
That's right; it start from <tr> and i did the same thing what you have recommended. Just Curious - Why don't we consider <tr> as root?
The <tr> tag needs to be nested in a <table> tag. For example, try loading this in your web browser:
<html> <head><title>test</title></head> <body> <tr><td>test</td></tr> </body>
If you load it in Chrome and look at the source with the inspector, you'll see that it strips the <tr> and <td> tags away, so that the text is a direct child of the <body>.