If your website has a hero image, make sure it loads and renders as early as possible. Many designs that feature a hero image suffer from HID (Hero Image Delay) mostly due to blocking scripts and stylesheets.
I’m right in the middle of building a hero imaged based site… and probably so are you (current web trend #3 for 2014/15). The problem is it can cause you site to appear to load slow. Fortunately Steve Souders is here to help you with some custom metrics to find how quickly it loads.An excerpt from Hero Image Custom Metrics