Specify image dimensions on the sidebars

Hey i’m trying to speedup my website by inputing good pratices. Everytime i run gtmetrix i always get an F on “Specify image dimensions” Their explanation is : “Specifying a width and height for all images allows for faster rendering by eliminating the need for unnecessary reflows and repaints.” I’ve resized the images to the right width/height (50 in this case for both) as well. And the code looks like this:

<img src=”url-to-the-image-here” width=”50″ height=”50″>

I have no idea why GTMetrix still complains about not specifying the width/height. Am i doing something wrong?