I really don't know how to add MP3 to my website.
I try asking and they gave me a code and so I pasted on. When I pressed it after, it didn't start downloading(oh yeah, I really like the kind that when people pressed it, it downloaded on to their computer then they listen to it), it took me to a page that says 'page not found' and 'bad gateway(or something like that)'

PLEASE HELP, THANKS

You would use the same link code as you would for a link to a webpage. But instead of going to the next webpage, the link will open the MP3 player in the web browser and the music will play.
<a href=http://www.yoursite.com/music.mp3>Click here to listen</a>

Before you upload your MP3 music file and add this link to your webpage:

<img src="/images/graemlins/wink.gif" alt="" /> Check the Terms of Use for your hosting company. Some hosting companies do not allow you to use MP3 files.

<img src="/images/graemlins/wink.gif" alt="" /> Also check the copyright of the MP3 file. You need permission to use a music file that is owned by someone else.

Upload/attach an audio file (. wav or . mp3) to your Google Site.
1. Go the the Page you would like to "attach" the audio file.
2. Click on Edit button.
3. Scroll to the bottom of the page to find the Add Files link.
4. Click on Add Files and locate the audio file you wish to upload.