Did you ever think how a single image can hurt your page load time. Well if ensured that image is added in pure unoptimized way, its can hurt a lot.
I recently experienced such an incident where an image was added. The image was visible at every page of the website. The issues with the image were
- External Site (Extra DNS to be resolved)
- No expiry headers defined
- Image not optimized
This caused our page load time to increase by almost 0.5 seconds. Notice the red circle (a sort of) where the image was added and site performance graph went up.
After a few days image was fixed by adding proper expiry headers and optimizing file size. The +ve impact was immediate as see in site performance graph.