Most important milestones for any effective impactful website do start from Appearance, effective marketing material / content, easy functionality and necessary utility features, SEO optimized website, responsive website which renders well on mobile devices aswell.
The above are more essential elements for a successful and impactful promising website.
Effective Appearance:
Your website should have professional look and feel, it should have nice layouted content, colors which go as per industry vertical which you are trying to promote through the website.
Play safe !! do not use too must of animation and effects as most of the users do not like animated website which takes time to load and instead they want to look at the website which has simple readable content which is easy to find being short and sensible.
Nice soothing colors, readable text, pleasing images based on topic which content is talking about.
Stunning Content:
Properly laid out content which is short and up to the mark; is what anyone looks forward to. Long contents are never ready by users and are often ignored.
Content should be properly laid out and not look creepy.
Nice lite Functionality:
Website functionality should be simple and self explanatory. Each feature which website should have should be of utility to the user and user should be able to understand how to use that since user will not read manual to learn how he has to use the website.
Simple Usability:
Website should be simple to be used and have fast page load time of less than 10-15 seconds depending on website type.
Site should have minimum page scroll and contents should be widely readable and menus should be approachable.
Website should be responsive so that it adjusts as per screen size and as per mobile screens.
SEO optimized:
Website should be SEO optimized so it can be indexed well by Google and remember if you feel that you can have a blog on the website for sharing sensible articles then do write them and have them on website. To help keep the user updated on latest trends and information and also help your website to rank better as a good article can gain great popularity and will lead the user to your website and help grow more business for you.