title: the css file stops working after a while
body: <p>My style.css file was working great (I checked my html file on web browsers and it appeared just the way I wanted) However, after a while, all web browsers stopped following some codes in the style.css file that had worked well just a couple minutes ago, even though I made no changes to those parts (particularly, those codes were the a hover, a visited). 
  I am using Audobe Dreamweaver CC and I am new to HTML and CSS.
  Thank you!
  _______________________________________style.css____________________________________</p>
  
  <pre><code> @charset "utf-8";
   /* CSS Document */
  #header{
      text-align: center;
      background-color: blue;
      font-family: Arizonia;
      font-size: 50px;
      color: white;
      padding: 5px;
  }
  h1{
      text-align: center;
      font-family: calibri;   
      font-size: 36px;
      color: red;
  }
  ul#nav1 {
      padding: 50px;
      text-align: center;
      list-style-type: none;
  }
  ul#nav1 li a: link {
      font-family: calibri;
      font-size: 25px;
      color: green;
      text-decoration: none;  
  }
  ul#nav1 li a: hover{
      color: orange;
      font-size: 50px;
      font-family:jokerman;
  }
  ul#nav1 li a: active{
      color: red;
  }
  ul#nav1 li: visited{
      color: white;
  }
  ul#nav li{
      display: inline;
  }
  ul#nav {
      padding: 20px;
      list-style-type: ||;
  }
  ul#nav li a: link {
      text-align: center;
      font-family: calibri;
      font-size: 10px;
      color: green;
      list-style-type: upper-roman;   
  }
  p.ul#nav li a: hover{
      color: orange;
  }
  ul#nav li a: active{
      color: red;
  }
  ul#nav li: visited{
      color: purple;
  }
  table, th, td {
      align-content:center;
      text-align:center;
      boder-spacing:5px;
      padding:10px;
      border: 3px solid green;
      border-collapse: collapse;
      font-size:20px;
  }
  .right {
      position:absolute;
      right:80px;
      width:auto;
  }
  </code></pre>
  
  <p>_______________________________________index.html____________________________________</p>
  
  <pre><code>&lt;!doctype html&gt;
  &lt;html&gt;
  &lt;head&gt;
  &lt;link rel="stylesheet" href="style.css" type="text/css"&gt;
  &lt;meta charset="utf-8"&gt;
  &lt;title&gt;Tự bạch của Trần Minh Triết&lt;/title&gt;
  &lt;/head&gt; 
  &lt;body&gt;
  &lt;div id="header"&gt;
  &lt;marquee&gt; Chào mừng đến với trang tự bạch của Trần Minh Triết &lt;/marquee&gt;
  &lt;/div&gt;
  &lt;hr/&gt;
  &lt;h1&gt;SITEMAP&lt;/h1&gt;
  &lt;ul id="nav1"&gt;
  &lt;li&gt;&lt;a href="background.html"&gt;Trần Minh Triết là ai?&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="milestone.html"&gt;Chặng đường tôi đã đi qua&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="gallery.html"&gt;Gallery yêu thích của tôi&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="contact.html"&gt;Hãy liên lạc với tôi&lt;/a&gt;&lt;/li&gt;
  &lt;li&gt;&lt;a href="makefriend.html"&gt;Tôi rất muốn biết về bạn, bạn nghĩ sao?&lt;/a&gt;&lt;/li&gt;
  &lt;/ul&gt;
  &lt;img src="index/footer.jpg" style="width:1366px;height:auto"&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>