如何在我的CSS中修復Parse錯誤[：]？

Question

這是與我在我的網頁開發課上進行的作業相關的代碼。 W3C的CSS驗證器不斷給我以下消息：「64解析錯誤[：]」。這是什麼，我該如何解決？請幫忙！

這裏是我的CSS：

* { 
    box-sizing: border-box; 
} 

body { 
     background-color: #ffffff; 
     color: #666666; 
     background-image: url(../images/background.jpg); 
     font-family: Verdana, Arial, sans-serif; 
} 

#wrapper { 
     background-color: #90c7e3; 
     width: 80%; 
     min-width: 700px; 
     max-width: 1024px; 
     box-shadow: 10px 10px 5px #888888; 
     margin-right: auto; 
     margin-left: auto; 
} 

header { 
     background-color: #000033; 
     color: #ffffff; 
     font-family: Georgia, "Times New Roman", serif; 
} 

h1 { 
     background-image: url(../images/sunset.jpg); 
     background-repeat: no-repeat; 
     background-position: right; 
     padding-left: 20px; 
     height: 72px; 
     line-height: 200%; 
     margin-bottom: 0; 
} 

nav { 
     float: left; 
     width: 160px; 
     padding-top: 20px; 
     padding-right: 5px; 
     padding-left: 20px; 
     padding-bottom: 0; 
     padding: 5px; 
     font-weight: bold; 

} 

nav a { 
     text-decoration: none; 
} 

nav a:hover { 
    color: #ffffff; 
} 

nav a:link: { 
    color: #000033; 
} 

nav a:visited { 
    color: #344873; 
} 

nav ul { 
    list-style-type: none; 
    margin: 0; 
    padding-left: 0; 
} 

main { 
     background-color: #ffffff; 
     margin-left: 170px; 
     padding-top: 1px; 
     padding-bottom: 1px; 
     padding-left: 20px; 
     padding-right: 20px; 
     display: block; 
} 

h2 { 
     color: #3399cc; 
     font-family: Georgia, "Times New Roman", serif; 
} 

h3 { 
    color: #000033; 
} 

dt { 
     color: #000033; 
     font-weight: bold; 
} 

.resort { 
     color: #000033; 
     font-size: 1.2em; 
} 


#homehero { 
     background-image: url(../images/coast.jpg); 
     height: 300px; 
     background-size: 100% 100%; 
     margin-right: 0; 
     margin-left: 170px; 
     background-repeat: no-repeat; 
} 

#yurthero { 
     background-image: url(../images/yurt.jpg); 
     background-size: 100% 100%; 
     background-repeat: no-repeat; 
     height: 300px; 
     margin-left: 170px; 
} 

#trailhero { 
     background-image: url(../images/trail.jpg); 
     height: 300px; 
     background-size: 100% 100%; 
     background-repeat: no-repeat; 
     margin-left: 170px; 
} 


footer { 
     background-color: #ffffff; 
     margin-left: 170px; 
     font-size: .70em; 
     font-style: italic; 
     text-align: center; 
     padding: 10px; 
} 

header, nav, main, footer { 
    display: block; 
} 

Answer 1

這是因爲nav a:link: { 與nav a:link {