The human brain relies heavily on visual cues, so providing consistency is a must for your website.
Not only should you provide familiar website elements (i.e. follow layout best practices for visual flow) that make the user comfortable with your site, but you should also carry the elements across the pages of your site.
When users are presented with something new or unfamiliar, they may internalize it negatively, even if only on a subconscious level. Utilizing different colors, fonts or layouts between pages can create a jarring feeling that can drive a visitor away from your web site.
Visual consistency, on the other hand, allows users to understand and better navigate your site to find desired information. This can entice a visitor to stay longer and engage more effectively with your business.
Learn more about the importance of visual consistency from DesignWebKit