Using Apache/1.3.26 (Darwin)
I had a hard time solveing this one and I saw a few other posts about it, so I thought I would pass on what I have learned.
I had a file index.html in my Users/myname/Sites folder, but when I went to 127.0.0.1/~myname/ I got a 404 error (File Not Found).
This happened because in my config.bak file the code said...
when it needed to say...
So when I overwrote my original config file with the provided config.bak I picked up this problem.
Because 127.0.0.1/~myname/ was looking for a folder named "public_html" rather than the Mac OS X default one of "Sites" as refered to in these tutorials.
So change "public_html" to "Sites" in your config file and stop and start Apache and then 127.0.0.1/~myname/ will default to your Sites folder.