Navigation not 100% on Vantage Premium

For some reason my navigation bar is no longer 100% of the browser width and I’m not sure why. I centered the text according to instructions I found on another forum and put the following code into the custom css:

/* Vantage Center the main menu */
.main-navigation ul {
  text-align: center;
}
.main-navigation ul li {
display: inline-block;
float: none;
}

The centering worked but now the navigation bar does not fill the whole screen. Even when I delete the added code, it still will not go back to normal.

Please help! Thank you!

URL: http://www.rideresponsibly.org/sub/