"CSS" stands for "Complete Scene Skip", which essentially means this. After collecting the flag to beat a level (on Android specifically), tapping the triangle arrow thingy will send you to the level select area, yet still completing the level. This exploit saves a lot of time, but it can only be done on Android, so those sub-categories are present.

What does CSS and No CSS mean?

hoboJimmy

Zanum

eqp8wpk5

arabic

FlowerBFDI

Bad Piggies

Normal, All Levels

Sandbox, 100%

Normal, 100%

No CSS

Normal

Alien

Ground Hog Day

Rise and Swine

When Pigs Fly

Flight in the Night

Tusk 'Til Dawn

The Road to El Porkado

All Episodes

1 Road Hogs

Find The Skulls

Find The Statues

Little Pig Adventure

Field of Dreams

Mode

CSS/ No CSS

Parts

Episode

Parts used

100% and alien 100% have been added as ILs categories

New Leaderbord Update

Android

Windows Phone

Macintosh

Angry Birds

Banned category?

Are glitches allowed?

How to speedrun?

Are power-ups allowed?

Are infinte money mods allowed?

do I need certain quality 

Biksel

Sami9999999999

Tegron

onesar

P00RGUY

WiiUOwner

RareMaw

jackzfiml

alboxer2000

Nathan0exe

BadPiggiesSpeedrun

Wide_Bug

NotSoMuchSpeedRunTe4s6