if that's how your writing it, then your doing it wrong in the css. Here's an example of one working:
templates/tmpl_{tmpl}/designbox_0.html
<!-- Design Box [ Start ] here -->
__designbox_content__
<!-- Design Box [ End ] here -->
templates/tmpl_{tmpl}/css/general.css
.NkBottomBg
{
position:relative;
background:url(../images/bottom_bg.gif) top left repeat-x;
top:8px;
left:0px;
margin:0px 7px 0px 7px;
width-expression:(100%-14px);
height:28px;
}
.NkBottomLeftB
{
position:relative;
float:left;
width:8px;
height:28px;
top:0px;
left:-8px;
background:url(../images/bottom_lb.png) bottom left no-repeat;
}
.NkBottomRightB
{
position:relative;
float:right;
width:8px;
height:28px;
top:0px;
left:8px;
background:url(../images/bottom_rb.png) bottom right no-repeat;
}
.NkDesignBL
{
position:absolute;
width:100%;
height:10px;
bottom:0px;
left:0px;
background:#96B2C9;
}
.NkDesignBr
{
position:absolute;
width:12px;
height:11px;
bottom:-1px;
right:-1px;
background:url(../images/design_br.gif) bottom right no-repeat;
}
.NkDesignBl
{
position:absolute;
width:12px;
height:11px;
bottom:-1px;
left:-1px;
background:url(../images/design_bl.gif) bottom left no-repeat;
}
.NkLeftBorder
{
position:absolute;
width:8px;
height:100%;
top:0px;
left:0px;
background:url(../images/left_b.gif) top left repeat-y;
}
.NkRightBorder
{
position:absolute;
width:8px;
height:100%;
top:0px;
right:0px;
background:url(../images/right_b.gif) top right repeat-y;
}
.NkDesignTr
{
position:absolute;
top:-1px;
right:-1px;
width:7px;
height:5px;
background:url(../images/design_rb.gif) top left no-repeat;
}
.NkTopMenuDevider
{
float:left;
width:6px;
height:27px;
background:url(../images/top_menu_devider.gif) center left no-repeat;
}
.NkTopMenuLb
{
position:relative;
z-index:800;
float:left;
width:13px;
height:28px;
top:0px;
left:-8px;
background:url(../images/top_menu_lb.png) top left no-repeat;
}
.NkTopMenuRb
{
position:relative;
float:right;
width:8px;
height:28px;
top:0px;
left:8px;
background:url(../images/top_menu_rb.png) top right no-repeat;
}
.NkTopMenuBg
{
position:relative;
height:28px;
top:-6px;
left:6px;
margin:0px 13px 0px 1px;
width:(100%-14px);
background:url(../images/top_menu.gif) top left repeat-x;
}
.NkDesignLb
{
position:absolute;
width:7px;
height:5px;
top:-1px;
left:-1px;
background:url(../images/design_lb.gif) top left no-repeat;
}
I'm not going to post the whole thing here, but there is a vast difference in the way the css is written between these, I won't interfere with your html file as I hate and rarely use html, but your css is way off and looks more like an html coder trying to write css.
Clean it up, organize it, start using standard format for css. Remember the ":" and ";" are your friends in css.