Using TextEdit to build web page source code

I have been using a PC to design web sites for years, but I recently purchased a MacBook Pro to use instead. On my Windows computer, I would use NotePad to create and edit .html files, which I could then just save and open in a browser. I have been trying to use TextEdit in the same way, but it doesn't appear to be working ... I just write the code into the app and then save it as an HTML file, but when I try to open it, what displays in my browser window is just the text.
I have edited my Preferences pane so that TextEdit is in Plain Text mode, and I've also disabled the automatic .txt file extension, but the problem persists. I have opened the .html file in FireFox, Safari, and Chrome, and they all display the same way.
Does anyone have any suggestions?

 

Downloaded TextWrangler and it appears to be working!
Thanks for your help.