According to the comments in config.php configuration file, you should not include a trailing slash in the URL for Moodle.
//=========================================================================
// 2. WEB SITE LOCATION
//=========================================================================
// Now you need to tell Moodle where it is located. Specify the full
// web address to where moodle has been installed. If your web site
// is accessible via multiple URLs then choose the most natural one
// that your students would use. Do not include a trailing slash
We are using IIS and it automagically appends a trailing slash. What web server are you using? Apache? Perhaps you might have to make a rule to redirect "http://<domain>" to "http://<domain>/" which can be done. But again on IIS it's not necessary as the web server wants the trailing slash and so it automatically redirects with a trailing slash.