Have you looked in your php error log? There should be something there. You can always go into the database and deactivate off the plugins. Here’s a link to do that: http://perishablepress.com/press/2008/02/18/quickly-disable-or-enable-all-wordpress-plugins-via-the-database/
thanks for your reply. When I think it over, it might have been after I automatically updated the wordpress version. now when I try to access the site, a blank page appears. how can I look in the php error log?
Using ftp rename the plugin you installed and try to go on your website
As I wrote, the error appeared after upgrading WordPress, not installing plugin as I said at first place..
if you have access to your admin panel, try deactivating all plugins. If you don’t have access to your admin panel, try manually resetting your plugins, using ftp rename plugins folder to plugins_hold and create a blank plugins folder If that resolves the issue, delete blank plugins folder and rename original back to plugins reactivate each one individually until you find the cause.
If that does not resolve the issue, try switching default theme (WordPress 3.0 and higher) to rule-out a theme-specific issue. If you don’t have access to your admin panel, access your server via FTP or SFTP, navigate to /wp-content/themes/ and rename the directory of your currently active theme. This will force the Default theme Twenty Ten theme (WordPress 3.0 and higher) to activate and hopefully rule-out a theme-specific issue.
If that does not resolve the issue, it’s possible that a .htaccess rule could be the source of the problem. To check for this, access your server via FTP or SFTP and rename the .htaccess file. If you can’t find a .htaccess file, make sure that you have set your FTP or SFTP client to view invisible files.
If you weren’t able to resolve the issue by either resetting your plugins and theme or renaming your .htaccess file, we may be able to help, but we’ll need a more detailed error message. Internal server errors are usually described in more detail in the server error log. If you have access to your server error log, generate the error again, note the date and time, then immediately check your server error log for any errors that occurred during that time period. If you don’t have access to your server error log, ask your hosting provider to look for you.
To get error log you will need log in on server abd click on error log icon or ask your host for help
