try adding display: inline; to the two css rules as hown here:
#outerWrapper #contentWrapper #leftColumn1 {
background-color: #ACCC6E;
float: left;
padding: 0px 0px 0px 0px; /* Sets the padding properties for an element using shorthand notation (top, right, bottom, left) */
width: 170px;
text-align: right;
display:inline;
}
/* Contains the main page content. When using a mutliple column layout the margins will be set to account for the floated columns' width, margins, and padding. */
#outerWrapper #contentWrapper #content {
margin: 0 0 0 170px; /* Sets the margin properties for an element using shorthand notation (top, right, bottom, left) */
padding: 0px 0px 0px 0px; /* Sets the padding properties for an element using shorthand notation (top, right, bottom, left) */
width: 790px;
height:610px;
background-repeat:no-repeat;
background-position:top right;
display:inline;
}
this will not affect any browser apart from IE6