Class " pull left" and "pull right" doesnt reflect in web page


I have added the class " pull left and pull right" to my ul elements with the correct syntax, it showed correctly once on the webpage then it went back to normal, it currently does not reflect on the web page . I know i have the correct syntax because I'm allowed to go to the next lesson, but I don't want to advance without the navigation links in the right places. Below is copy of my code

<!DOCTYPE html>

    <link href="     /shift.css" rel="stylesheet">
    <link rel="stylesheet" href="           -content/courses/ltp/css/bootstrap.css">
    <link rel="stylesheet" href="main.css">
    <div class="nav">
      <div class="container">
        <ul class="pull-left">
          <li><a href="#">Name</a></li>
          <li><a href="#">Browse</a></li>
        <ul class="pull-right">
          <li><a href="#">Sign Up</a></li>
          <li><a href="#">Log In</a></li>
          <li><a href="#">Help</a></li>


The problem you are seeing is because of those extra spaces in the shift.css and bootstrap.css URLs. Those spaces are breaking the URLs.