Broken or not clear font in qt applications

[Dcqt]

Hi have installed Qt newly , it got installed successfully.
But when i run any applications the font in the application windows is broken or not clear.

Can any body suggest me how to resolve it.

i have gone through below sites but i cannot understand anything there and there it is no mentioned how to solve it.

https://bbs.archlinux.org/viewtopic.php?id=166034
https://bbs.archlinux.org/viewtopic.php?id=69336
https://bbs.archlinux.org/viewtopic.php?id=67031

some sites mention that "Turn off 'Sub-pixel rendering" ,but how , i dont know where to do this .

please help..