“Website speed and page load time are important as any other factor that impacts search engine rankings.”
The website hosting provider you choose has a huge impact on your page load times. Pick dedicated hosting solutions over shared hosting to avoid other websites slowing down your site on shared servers.
CSS holds the style requirements for your page. Generally, your website accesses this information in one of two ways: in an external file, which loads before your page renders, and inline, which is inserted in the HTML document itself. When setting up your styles, only use one external CSS style sheet since additional style sheets increase HTTP requests.
Oversized images take longer to load, it’s important to optimize your images for the correct size (under 300kb is ideal).
I recommend using an image editing tool (my favorite is Photoshop), albeit a designers tool. You can also use Preview (installed with Mac OS by default).