.PNG background won’t go transparent

Hi there, I’m trying to create a header for my site and I’m trying to use a .PNG format as I want the background of the Header to be transparent. I’ve created the header image file in Photoshop CS2. It’s simply my name in a graffiti style font that I found online and installed into my Wondows/fonts/ directory. I then switched off the background in Photoshop using the ‘Layers’ controls on the right hand side and changed the text to yellow. So now… as far as I can tell everything should be ready for me to save/ export the file as a .PNG and upload it to Weebly to put into my site. However, when I upload it… it looks perfect for a second or so until I close the ‘Edit Image’ window and then it suddenly imposes a black background onto the image and somehow slightly distorts it all as well Here is the URL: -http://liamorourke.weebly.com/ As you can see it is the main header that says: ‘Liam O’Rourke’ in yellow writing… obviously with that horrible black background. If anyone can work out what I’m doing wrong here I will love you forever… Obviously in a Nerdy platonic way thanks guys.