Usability is a qualitative indicator of the simplicity and convenience of using website.
So, there's bacis rules of the site usability:
Website have to be readable. It means a well-chosen font, size and color. It's better to use a dark text color on a light background. So the user'll understand your information more clearly and he will spend more time on your site.
You need to present relevant and useful information so that the user can quickly find it. Therefore, the basic information should be placed on the main page, because the visitor won't visit all 20 pages of your site in search of the required information, it's easier for him to go to another site.
Now the subscription buttons on the page are very popular. The most optimal place for their placement is the sidebar.
Placement of elements on the site
All the main elements of the site, such as the main menu, contacts, logo, search are better placed standardly, as on another sites. Since it's the optimal placement, Internet users are already accustomed. In this case, you don't need "to invent a new bicycle".
Making an order or registering on the site
As it's tedious procedure for registering on the site or ordering, you need to fill a million fields and it isn't a fact that from the first time all fill in correctly. Therefore, we advise you to include only the main fields on the order pages, which are informationally important. For example, name, phone, address and e-mail of the user.