Fix an RSS issue

My site is avelim.co.il. The site is on Hebrew wordpress 3.4.1, using the theme Weaver 2.2.6 with many customization done by programmers. The programmer should do the work a test site and then on a live site. I run the rss feed of muy site at w3 c feed verifications service [login to view URL] I get the notice: This feed is valid, but interoperability with the widest range of feed readers could be improved by implementing the following recommendations. Your feed appears to be encoded as "UTF-8", but your server is reporting "US-ASCII" I want this fixed The work should be done in 24 hours after being awarded the project. Freelancer should allow 10 days for testing after he finishes his work, before getting paid.