CSS responsive layout, with elements fluid and fixed

Hello World!

I need a bit help, I am developing a custom theme for WordPress: https://bjorn.flabifitness.hu/

I need a fixed header, footer, menu area. And a fluid content area with page content (an image).

During browser window size is changing, only the content need to be changed/adjusted to view-size, without scrollbar, but picture wanted to be attached to footer as well.

This is my CSS-code for now: (main: all of page, inside header, container(sidebar, content), footer)

#header {
	background: #1d1d1d;
	padding-top: 15px;
	padding-left: 35px;
	padding-bottom: 13px;
}
#logo {
	background: #1d1d1d;
}
#footer {
	clear: both;
	min-width: 100%;
}
.container {
   height: auto;
   overflow: hidden;
}
.sidebar {
    width: 242px;
    float: left;
    background: #434343;
	min-height: 92%;
}

.sidebar a{color:#999999;}

.content {
    background: #434343;
    width: auto;
    overflow: hidden;
}
#img {
  width: 100%;
  height: auto;
}