The entire Portal is optimized for use on mobile devices.
No matter if you want to use it on your tablets or mobile phones everything will display in fast and organized way.
By default your selected Forum style will be used on mobile devices as well.
Of course that is not always the best option when the sun is shining on your display.
That is why you can enable a bright style just for use on mobile devices. You can enable this option on your "General Settings". The option is called "Enable predefined mobile style".
This bright style is only active when you are using the Portal on small displays such as tablet or mobile phones.
It has no influence on the style setting for your Desktop PC.