How to see/change screen refresh rate or monitor frequency?

Compiz looked like it worked. But it didn't work.

So the solution to this is the following.

First we check available modes.
$ xrandr
1440x900       59.9+*   75.0
1280x1024      75.0     60.0

Then we pick the mode, including resolution and refresh rate.
$ xrandr -s 1440x900 -r 75

Or just the refresh rate
$ xrandr -r 75

Let's see if it worked
$ xrandr
1440x900       59.9+    75.0*
1280x1024      75.0     60.0

Alright. Then all you have to do is add the command to Startup Applications and be done.

open your terminal and type this

sudo apt-get install compizconfig-settings-manager

then type compiz in your unity dash , it will list you compiz settings manager .Open compiz and at general options click at composite and there you have untick the detect refresh rate then you can manually set the value you want . .

and two know allowed refresh rates for the resolution you can use xrandr

the second row are allowed refresh rates with respect to the resolutions . so by depending on resolutions you have set , you can change the refresh rate by using the above methods .