The Need For Speed:

No matter how user-friendly and intuitive your web design is, if it takes forever to load, no one is going to care. Great mobile websites take into account the processing power of the devices accessing them and size their content accordingly.

So what exactly are we downsizing?

Generally speaking, the more HTTP requests a device has to process, the longer it is going to take to load.
Everything from style sheets to links, to backgrounds and images all, present themselves as HTTP requests that will potentially slow your loading speed to a degree that visitors will abandon ship for a faster experience.

However, we can change that by being smart about the content we include in the design. This goes back to the relevant content we were discussing earlier, the same law applies here.
When including files in your design, make sure that they are truly relevant to mobile users. That way your content remains uncluttered while you decrease the number of potential HTTP requests.

Images are among the most significant users of bytes per page, thus by optimizing your images, you stand to experience a noticeable boost in download speed.
A simple tip to optimize your images is to include only the most relevant, as well as appropriately sized. Because mobile screens are much smaller than standard desktops, heavier high-resolution image files are displayed as being much smaller anyway, while taking far longer to load. Learn to strike a balance between the appropriate size for mobile screens and quality. Usually, websites can get away with using a lower resolution image, saving valuable processing time and memory.
Moreover, use images wisely, and do not embed SEO content in them, as Google and other SERPs do not read images when ranking content.

In addition to reduced image sizing, consider limiting your use of JavaScript and other interactive effects, as they too require several HTTP requests while not usually being invaluable to your web experience.

Compression is also a great way to reduce HTTP request processing time.
Today, all browsers are able to recognize and read compressed HTTP requests, usually referred to as gzip files. These files are lighter than non-compressed files, resulting in faster network transfers.
However, this technique only supports text files such as style sheets and other relevant code, and unfortunately, cannot be used to compress image files.