make header image transparent in "twenty ten" theme

I am trying to make the header image transparent within my site. If you view my site you can see that my header has an image of my “Dj Dopestar” logo. However, this header has a black background. I want the image to be transparent and only the letters to show

I followed the recommendations within this thread:

I changed the css coding to the folliwing:

#wrapper {
margin-top: 0px;
background: #fff; –>I removed this
padding: 0 0px;
}

#main {
background: #fff; –>I added this
overflow: hidden;
padding: 40px 0 0 0;
}

However, despite these changes, whenever I upload my image there still seems to be a black background! I would really appreciate any help because this is very annoying! I am getting a new Dj Logo designed and I want to resolve this soon so I can finish designing my site!

Thanks,
Dj Dopestar