Better Performance by putting image dimensions YSlow advises that all images should have dimension attributes even if they are presented at 1:1 scale, so that the browser knows the dimensions before the images are loaded, to start rendering the page faster.

I have a view of 20 taxonomy titles and their image fields. How I can make Drupal put their dimensions attributes on each image html tag?

I have drupal 7.
This is a known issue in Drupal 7. A conscious choice, as it were, from the issue Remove unnecessary I/O from theme_image().

There is a patch to fix this here: Images are not printed with height and width.