Clarification of Plane Wave Solutions

some1rational

Hey guys, I'm new here and I just had a quick question about plane waves.

http://www.brainflux.org/java/classes/PlaneWave.html

This java applet for plane waves has in it's description "Chose a sign-convention from the four equations (see how two are not plane waves)." I'm confused because it appears all four cases are plane waves. Am I not reading that line correctly? or are two of them really not plane waves?

Thanks for any input!