Salesforce allows us to create feed-based page layout on Leads, Account, Contact, Opportunity & custom objects. See this documentation for more information – https://help.salesforce.com/HTViewHelpDoc?id=create_feed_based_layouts.htm&language=en_US
However, once feed-based page layout is enabled, you are no longer able to revert it back to the normal page layout view. However, You can try below workaround:
- Create a new page layout
- Choose existing page layout (the feed-based layout)
- Do not check the feed-based checkbox
Once new page layout is created, remember to assign the page layout to profiles & record types.