background image for navigation link

background image for navigation link

I am trying to display a background image behind the navigation link, but
it is not displayed completely this is the code:
#aboutlink{
background-image: url(sidebar.png);
background-repeat: no-repeat;
background-position: left;
background-color: transparent;
display: block;
margin-bottom: 160px;
text-align: left;
}