#flowersright {
background:url(../images/bg_flowers_right.png);
width:88px;
height:380px;
position:absolute;
right: 7%;
}

Also, when adding a property to #mainWrapper, add it to the individual #mainWrapper declaration. Adding it to the group declaration gives the same property to all of #navColumnOneWrapper, #navColumnTwoWrapper and #mainWrapper; this probably won't make a difference here, but it often will mess something up. If there were no other #mainWrapper declaration, you should separate this one from the other two:

#navColumnOneWrapper, #navColumnTwoWrapper {
margin: auto;
}

#mainWrapper {
margin: auto;
position:relative;
z-index: 100
}

but since there already is one at the top of the /*wrappers*/ area, just put all its properties there.

Not sure why you changed #navMainWrapper, as this should not be necessary for this purpose.