Discuss the differences between Named skins and Default skins ?

Answer:

Here are some of the differences between Named skins and Default skins.

Default Skin: This type of skin will be applied to all the controls which are of same type when a theme is applied to a page. If a control does not have a skinID attribute, then that control skin is a default skin.
Example:
If you create a default skin for a Calendar control, the control skin applies to all Calendar controls on pages that use the theme.

Default skins are matched exactly by control type, so that a Button control skin applies to all Button controls, but not to LinkButton controls or to controls that derive from the Button object.

Named Skin: These type of skins do not apply to the controls automatically by type. This named skin is a control skin with a SkinID property set.By creating named skins, you can allow to set different skins for different instances of the same control in an application.