mod_rewrite

I'm  looking at some tutorials for mod_rewrite and I am trying to replicate a simple example:

In my .htaccess file I put this:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_ACCEPT} text/html
RewriteRule \.html$ - [T=text/html;charset=utf-8]
RewriteRule ^old\.html$ new.html [R]
</IfModule>

When I access http://mywebsite.host.org/dir/old.html

It redirects me to http://mywebsite.host.org/home/myname/public_html/dir/new.html

Why is this? How do I fix this? I've been looking all over the internet and Google turns up absolutely nothing.

Disregard the invisible teenager's posts