When I look at any web site on my iPhone its format is usually optimised for the small screen, however recently I have recently started noticing this mobile format appearing when I visit certain web sites on my Mac. I have attached two examples below, and these particular sites appear to have no link that I can click to switch to the desktop version.

Do I need to approach the web site owners to ask them to fix this, or is there some setting on my computer that I need to change?