How can style elements be applied? (similar to a CSS file/skins)

Answer:

Styles elements are supported in the form of application resources. An app.xaml file can be created containing an application resource Xml construct. The target type for each style is set to the control on which the style needs to be applied.

App.xaml:
<Application.Resource>
<Style x:Key="MyBorder" TargetType="Border">
<setter property="width" value="5">
</style>

Page.xaml:
<Border Style="{StaticResource MyBorder}">
...
</Border>