Try adding float:left; to each respective box.
What this does is that it floats the div to the left so that other content appears next to it. If you do this to the three boxes, they will hopefully appear next to each other.
Here’s an example:
#content {
width: 600px;
}
#leftbox {
width: 200px;
float: left;
}
#middlebox {
width: 200px;
float: left;
}
#rightbox {
width: 200px;
float: left;
}
I did not exactly understand which part of the code you pasted you needed help with, but I hope this helped you out.