The style application toolbar allows you to create and modify styles automatically. This tool window works in two modes "Auto mode" and "Manual mode".
The Auto mode is targeted for users who are new to CSS and in this case Visual Studio will control where the newly generated styles will be placed.
Manual mode is prescribed for experienced users. In Manual mode users can control where the style have to be placed by specifying the "Target Rule". The target rule shows the following options in the drop down for a selected control: .ClassName(Current Page), < Inline Style >, (New Auto Class) and Apply New Style…
SDET, Web Development Tools