css - Why Won't My Simple Icons Appear? -

I am working on the "flat design" website, and I have decided to use social icons. I wanted to keep the background of the successful icon deep, while the white overlay image remains the same. Therefore, I made a list (this is a navbar). I have put an anchor inside the list item. I tried to set the background image as anchor in the form of anchor and the background color of the list item, whatever I wanted to do I changed the background color to list item transition Tried to add, but he did not work so I got rid of it. Here's the CSS for the entire piece of site:

  div # nav (float: right; width: auto; height: 37px; paddle-top: 15px; paddle-right: 15px; padding- Bottom: 5px; background color: RGBA (100,100,100,0.3); border-left-color: RGBA (255,255,255,0.2); border-right-color: RGBA (255,255,255,0.2); border-right-width: 1px; border -right-style: solid; border-left-width: 1px; border-left-style: solid; border-top-width: 1px; border-top-style: solid; border-top-color: RGBA (255,255,255,0.2 ); Margin Top: 102px; margin-left: 2px;} #nav ul {padding: 0; Survey Style: None; Margin: 0;} # nav ul li {width: 32px; height: 32px; margin-left: 15px; display: inline-block; background color: # 000000; range: 0;} # Nav ul li a {z-index: 10;} #facebook {width: 32px; height: 32px; background image: url ('images / facebook.png');}   
 and Here is the HTML:  
  
  ul> 
 
 an id = "Facebook" & lt; Gt; & lt; / a & gt; & lt; / li & gt; & Lt; Li & gt; & Lt; An ID = "Twitter" & gt; & Lt; / A & gt; & Lt; / Li & gt; & Lt; Li & gt; & Lt; An id = "youtube" & gt; & Lt; / A & gt; & Lt; / Li & gt; & Lt; / Ul & gt; & Lt; / Div & gt; In CSS, I did not include the style for the ID "Twitter" or "YouTube" because I'm just trying to work with it one. Can a simple icon show up and work in transit? I will provide a simple icon Icon Images are inside a folder named "Picture" inside a folder named "_css", which contains the CSS file.  
   
 
 
 add  
  display: block ;   
  
 for your anchor the anchor tags appear naturally inline and since you do not have any content in the anchor, even if you give them dimensions Will not see them