Internal Server Error urgent help please!

I went to check my website and i received this error :

“Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, webmaster@xxxxxx.com and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request. “

How can it be fixed? Its rather funny, i cannot access the main domain e.g. http://www.domain.com however i can fully access http://www.domain.com/wp-access.com . I have deleted my database, reinstalled wordpress and i am getting the same problem, i heard it might be the htaccess? this is mine (not the wordpress one)

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

<Files php.ini>
order allow,deny
deny from all
</Files>

suPHP_ConfigPath /home/xxxx/public_html
<Files php.ini>
order allow,deny
deny from all
</Files>

(anything wrong with it?)

Also what is suPHP? i was searching though QNA from the host and i came accross this, he had similar problems im not sure if he had wordpress ..
“
Unfortunately, the temporary url will not work with suPHP servers like the one you are on. This is a security measure put in place by suPHP to prevent others on the server from accessing your files “

Thanks for any help on this matter.