What is the most important part of a website?

The most important part to any website is content. Without content, your website is nothing more than an advertisement, which is not an effective online marketing strategy. The goal of any marketing professional that designs websites should always be to create an online resource for people.
Whatever your product or service is, your goal as a business or organization should be to empower your visitors, not simply sell them something; that will come in time. By showing that their interests are important to you, they have a reason to return, thus increasing the likelihood of a purchase or additional purchases.

Make sure to have the following:

• Detailed product descriptions.
• In depth product support information.
• A responsive technical support section.
• Easy to find contact information.
• Product manuals, white papers, sales sheets, user manuals, etc.