You can avoid having too many pages in your main navigation menu by dividing your site up into categories and subpages. You have a few options available to help with this.
1. Upgrading to Yola Silver or Yola Gold allows you to create submenus quickly and easily. For more information, please see this tutorial: Creating Submenus
2. Using Flyover Menu feature. This allows you to create a second-level vertical menu in a flyover format. Please see this tutorial.
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5-minute website fixes: Clean up your website navigation with flyover menus