HTML5 placeholder attributes can be leveraged to provide a convenient means of indicating required input formats.
By default, browsers typically implement placeholder attributes as light-grey text. As with all default user agent styles, one will feel compelled to define custom selectors to provide application specific styles to elements, placeholder attributes included.
Styling Placeholder Text
Styling placeholder attributes on input and textarea elements is rather simple; however, one should take care to keep style declarations limited to those of a textual nature; e.g.
Placeholder attribute text can be styled for all supported input element types (text, search, url, tel, email, and password) as follows:
As can be seen, defining styles for placeholder attribute text is quite simple, and such styles can be employed to add subtle enhancements to form elements in modern web apps quite nicely.