If you have a webhosting package at 1und1.de you may face some problems while using mod_rewrite for a website located in a subdirectory.
For example, if you create a subdirectory
/mywebsite/
and place your website (e.g., typo3 or something else) and a .htaccess file inside this. And if you try to use mod_write to have search engine friendly URLs or just rewrite urls for any other purpose, you may end up with a 500 internal server error.
To fix this problem, you should open your .htaccess file and check your RewriteBase configuration.
If your website is located in a subdirectory of your webspace, you need to set the RewriteBase configuration to:
RewriteBase /
For Example, if you want to configure the .htaccess file shipped with Typo3, and your installation is in a sub-directory “/mywebsite/”, you should modify the file as shown below:
### Begin: Settings for mod_rewrite ###
# You need rewriting, if you use a URL-Rewriting extension (RealURL, CoolUri, SimulateStatic).
...
# Enable URL rewriting
RewriteEngine On
# Change this path, if your TYPO3 installation is located in a subdirectory of the website root.
RewriteBase / # <= The important part of the configuration
...