At last OpenGL Extension Viewer admits that there is OpenGL 3.1.
Thank you Stefan!
It will be nice if OpenGL Extension Viewer can change the way it verifies GLSL version on NVIDIA GPUs. Currently supported version of GLSL on my GPU is 1.40 NVIDIA via Cg compiler, but OpenGL Extension Viewer says that even ver. 1.10 is not supported.
There is one minor bug in section Rendering tests. Only test 3.0 can be executed, even if checkbox All is checked.
Nevertheless, Extension Viewer is great! Keep on, guys!