QUESTION REGARDING UNICODE WARNING

Sir,      Taking a HTML course at Owens Community College, I am working on my final project.      Using the your validator I am getting warnings for some of the Greek letters I am using in my HTML file, such as ω σ γ and &lamba;..  The warning says, "Text run is not in Unicode Normalization Form C.  The Web page looks good when run though.      I imagine I have to declare this as some kind of font or charset.  Hope you can help me. Leo Rose