ehhe, I'm afraid the only way to remove the ad is to upgrade to a paid plan. Often you need to invest somethings before gaining any profit.
I pay 3 years for premium but now i'm run out of money. The site changed to free and my users leave my site because this type of UCOZ ad. This is a problem!
The most used resolution worldwide is 1366x768: http://gs.statcounter.com/#resolution-ww-monthly-201412-201505
In this resolution my users UNABLE to login and search content because HIDE the ucoz ad. I know i able to edit the template and move this things to another area of page but this is INSANE.