Visual weight is the term used to describe the visual "loudness" of a design element (banner, logo, image etc) on a page. When you glance a at a page you will usually notice some parts of the page before others. While page position has something to do with this, usually the first elements you notice will be the loudest.
Making something larger, brighter, darker, or of higher contrast or a hotter colour are the usual ways to give something greater visual weight
Because their eye is drawn to weightier items first these are often the elements that website users use to anchor themselves in a new page and make sense of it. Its important that the highlighted elements actually give the right information to the user, else the page risks confusing and frustrating users, and encouraging them to leave.
Equally if there are several elements of equal weight on the page (ie. there is no clear hierarchy of weight) then users are forced to make a decision about what element is the most important. This sort of uninformed decision making is quite stressful and once again will encourage users to leave your page and never return.

Diagram from http://www.lukew.com/
So its important to have a hierarchy of visual weights on a page. But its also important that the weights of the page elements reflects your website's strategic goals and the needs of the site users. To calculate this we use the following exercise:
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