Do not modify the DOM when traversing
Modifying the DOM (Document Object Model) as you traverse it risks making the loop highly resource-expensive, especially in terms of CPU usage. An infinite loop, which consumes a huge amount of resources, might be generated if we add elements at the same time as we traverse it. It is thus highly recommended to NOT perform such edits.
Keep the number of domains serving resources to a minimum
When a website or online service hosts a web page’s components across several domains, the browser has to establish an HTTP connection with every single one. Once the HTML page has been retrieved, the browser calls the sources as it traverses the DOM (Document Object Model).
Some resources are essential for the page to work. If they are hosted on another domain which is slow, it may increase the page’s render time. You should therefore, when possible, group all resources on a single domain.
The only exception to this is for static resources (style sheets, images, etc.), which should be hosted on a separate domain to avoid sending one or multiple cookies for each browser GET HTTP request. This reduces response time and unnecessary bandwidth consumption.
