html - how to specify image size in pixels

Question

Quick question about specifying the size of images in pixels:

<img src="/logo.jpg" alt="logo" width="200px" height="120px" />

or

<img src="/logo.jpg" alt="logo" width="200" height="120" />

I've been always putting in the px but recently noticed that very few people do this. Am I better off leaving that out? Does it matter one way or the other?

Answer 1

As far as I know, you do not add the px label to width/height attribute values on the img tag itself, and I believe (though could be wrong) it's because pixels are used regardless. In CSS, however, one may use different units to specify width and height, therefore it is appropriate to add the label when using CSS.