You can customize the page layouts for record detail and edit pages, Self-Service portal pages, Salesforce Customer Portal pages, and the case close page. Page layouts control the layout and organization of buttons, fields, s-controls, Visualforce, custom links, and related lists. They also help determine which fields are visible, read only, and required. Page layouts can include s-controls and Visualforce pages that are rendered within a field section when the page displays. You can control the size of the s-controls and Visualforce pages, and determine whether or not a label and scroll bars display.
The enhanced page layout editor is a feature-rich tool that allows you to customize your organization’s page layouts for detail and edit pages in AdvoLogix and the Client Portal. The enhanced page layout editor provides functionality in an easy-to-use interface.
The enhanced page layout editor consists of two parts: a palette on the upper portion of the screen and the page layout on the lower portion of the screen.
The palette contains the user interface elements, such as fields, buttons, links, related lists, and any additional elements that are available for you to add to the page layout.
Navigate to Setup
Click on Your Name
Go to one of the following areas to edit the page layouts of Accounts, Contacts, Activities or other Standard objects in the system
To Edit Custom Objects page layouts, after you click on Object link, you will need to select the object to your wish
Click the name of the object in the list.
Click on Page Layouts.
Click on New button
Existing Page Layout
As an option, you may select an existing layout to clone.
Page Layout Name
Give a name to this new layout
Drag & Drop the Fields, Buttons, Custom Links, Visualforce (VF) pages or Related Lists on to the page layout detail section.
For further information, See Force.com's: Customizing page Layout with the Enhanced page Layout editor