what am I doing wrong? It does not work and that's it: (you need to hover so that the color is superimposed on the picture. I probably do not know the trick :)
img:hover { background: rgba(39,156,232, 0.5); cursor: pointer; } <div class="head_block"><img src="http://lorempixel.com/output/city-qc-360-260-1.jpg" alt="" width="360" height="260"></div>