[Wordpress][Solved] Fix the Internal Server Error in WordPress

Firstly, I think I should talkabout my case first:

I installed wordpress in a folder named "ffftest", and the folder is placed at root.
One day, I make the domain point to the folder "ffftest",
That means I input "http://www.ffftest.com/ffftest" before to access wordpress index page,
And Now I am able to use "http://www.ffftest.com/" to access wordpress index page directly.

It's sure that I need config the path in database but I missed that :
Change this file, ".htaccess" which is placed in the root of your wordpress.

From this: (the text in red is your old path)

# BEGIN WordPress
RewriteEngine On
RewriteBase /ffftest/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /ffftest/index.php [L]

# END WordPress

To this: (the text in green is your new path)

# BEGIN WordPress

RewriteEngine On
RewriteBase /ffftest/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress

my wordpress's root directory is "http://www.ffftest.com/ffftest" before
"/ffftest/index.php" means  http://www.ffftest.com/ffftest"
my wordpress's root directory "http://www.ffftest.com/" now,
So I use "/index.php" now,
"/index.php" means  http://www.ffftest.com/"

You can see is there sth wrong in wordpress's .htaccess file