Images stretched horizontally in mobile lay-out

In a CBC I use an image as level:

<center><img src="[%GraphicsPath()%]check.png" alt="" border="0" width="18" height="18"></center>

This works fine on desktop. But in the mobile lay-out it is resized. The image is stretched horizontally. I've tried solving this in the img tag and/or in the css but no succes so far. Is there a solution for this?

[UPDATE]
I have found a solution.

<center><img src="[%GraphicsPath()%]check.png" alt="" border="0" width="18" height="18" style="width: 18px !important; height: 18px !important"></center>

Not sure if real front end developers will approve but it works.

Resolved