Syntax error

Hi there,

just started my first time doing css. So far I just copied two codes - but now, when I want to put a new code in, it says syntax error. 

I want to put a code in that makes a hover effect at the header buttons...but as soon as I type in .header it says syntax error....

Any help will be highly appreciated.

/* Change dropdown menu background */
.header-nav-folder-content {
   background: #454545 !important;
}

//Stylized Folder Dropdown Menu
@linkBGColor: #ffffff;
@linkTextColor: #7C8C0A;
.header-nav .header-nav-item--folder .header-nav-folder-content {
  padding: 0;
  .header-nav-folder-item {
    padding: .5em 1em;
  }
  .header-nav-folder-item:hover {
    background: @linkBGColor;
    a {
      color: @linkTextColor;
    }
  }
}

I want to put a code in that makes a hover effect at the header buttons...but as soon as I type in .header it says syntax error....

Just tested above code on my site. No syntax error..

I think it's working now. Thanks though!!!