Ubuntu 12.04 fonts not clear due to back ground colour
 

After upgrading to ubuntu 12.04 ,fonts appear in white colour.So it is difficult to read the fonts in white background.How to correct this problem.I have attached a screen shot with this.

It looks to me that you're using a custom theme. Not the original Ubuntu one. I'm using Mint, but changing themes, color schemes etc. occasionally messes up font colors here as well.

Try setting your Mac theme back to the default Ubuntu one and see if that makes a difference.