Guide:
#container
{
background-color:rgb(62, 157, 153);
}
in other words:
#container
{
background-color: rgba(red, green, blue, alpha);
}
rgba(255, 0, 0,1) is red
rgba(0, 255, 0, 1) is green
rgba(0, 0, 255, 1) is blue
alpha (transparency) takes values from 0 to 1, therefore
rgba(255, 0, 0,1) is fully opaque (not transparent)
rgba(255, 0, 0,.5) is 50% transparent
rgba(255, 0, 0,0) is fully transparent