Creating a custom master page provides the greatest flexibility for branding a SharePoint Implementation. However, there are many hidden traps to be aware of when creating a custom master page. For example, it is usually best not to start from scratch but to use a copy of the v4.master or starter master page http://startermasterpages.codeplex.com/ created by Randy Drisgill.
The v4.master is the new default master used for SharePoint 2010 and creating a new custom master from a copy of the original v4.master will ensure the inclusion of expected SharePoint 2010 User Experience Functionality.
After deploying a custom master page based on the v4.master we began seeing a “You must specify a value for this required field” message box whenever trying to edit or add new list items and perform other routine tasks.
After much research the solution was found on this blog post: http://blogs.msdn.com/b/tmathis/archive/2010/03/18/you-must-specify-a-value-for-this-required-field-error-when-hidding-placeholderpagetitleintitlearea.aspx
It has always been a good practice to place unused content place holders within a hidden ASP.NET Panel Control. However, the message box error was caused by the PlaceHolderPageTitleInTitleArea content place holder being contained within an ASP.NET Panel Control with the hidden attribute set to false. The resolution was to remove the hidden=false attribute and hide the ASP.NET Panel using a CSS Style. The style can be simply added to the master page for easy deployment.