Although we may build a great site that works well across multiple devices, it's still no good if it is slow! Every website will of course operate differently, but there are a number of factors to allow for, which can affect page (and site) speed:
Downloading data unnecessarily: On a responsive site, we may hide elements that are not displayed on smaller devices; the use of
display: none
in code means that we still download content, even though we're not showing it on screen, resulting in slower sites and higher bandwidth usage.Downloading images before shrinking them: If we have not optimized our site with properly sized images, then we may end up downloading images that are larger than necessary on a mobile device. We can of course make them fluid by using percentage-based size values, but if the original image is still too large, this places extra demand on the server and browser to resize them.
A complicated DOM in use on the site: When creating a...