I don't understand my errors (validator)

Question

I checked my html and css in a validator and I don't understand my errors.
For html:
Line 22, Column 32: An a start tag seen but an element of the same type was already open.
                      <li> <a href="index.html">portfolio </a></li>
And for CSS:
Value Error : background-image attempt to find a semi-colon before the property name. add it
Parse Error :(../images/linkedin-logo.png)
.button-linkedin {
          background-image: url:(../images/linkedin-logo.png);
          height: 3rem;
          width: 3rem;
          float: right;
          margin-top: 4.5rem;
          margin-right: 3rem;

Answer 1

You have an unclosed <a> tag somewhere higher up in your code.  Look at your pinterest link which I spotted on line 16 from another discussion.
http://forums.adobe.com/message/5267843#5267843
In your CSS, change this:
url:(../images/linkedin-logo.png);
to this -- no colon between url & parenthesis:
url(../images/linkedin-logo.png);
HTML & CSS Tutorials -
http://w3schools.com/
Nancy O.