User Cannot Edit Item

Valid for Sitecore 5.3

The following list suggests possible causes, starting with the simplest and most probable.

Did the user select the Edit button?
Only Administrators can edit items without enabling the action. All other users must select the Edit button () to start editing something.
Does the user have access rights to the Item?
An Administrator can use the Access Viewer to check whether a user has write permission for an item. If a user cannot see the item at all, it may mean that the Read permission is also denied.
Has someone else locked the Item?
Only one user can edit the item at a time.
Is the Item in a Workflow State that the user does not have access to?
Security rights can be influenced by the workflow mechanism. When an Item is in the workflow, effective security permissions for users in some cases will be determined by the current workflow state of the Item. For example, if an item is in the 'Approving' state of the 'Simple' workflow, a user must have 'write' permissions for the 'Approving' state in order to be able to modify the item.

For instance, an item submitted by an editor to the next workflow stage will not be accessible for this editor until someone returns it to the initial state. Please, refer to the Workflow Commands section for more information.