Search engines use these with great weight when deciding which pages to return as a match for a search. What choices made here greatly affect how often your page is visited from a search engine site. Your page will look tremendously different to different people. The word tremendous is not used lightly here. Some pages are hard to read in 256 color mode.
Some browsers display all pages with a white background and black text.
Laptops often use smaller 640x480 screens. Some browsers don't even display images. Be aware that a given page may appear tremendously different to different people. Considering trademarking your domain name'. Courts have recently decided that no one actually owns a domain name.