It looks like you are putting it in between the left and rite columns that are floated. It looks like if I add a float left to the form css it adjusts it properly.
This setting is in this css file:
CSSFormBuilder/FD_Standout_Default.css
In here on line 83 is this style, add in the float left here like this:
form.Standout_Default {
background-color:#999999;
font-family:Futura,"Trebuchet MS",Helvetica,sans-serif;
font-size:11pt;
padding:60px;
width:20em;
float:left; /* this is the float that was added */
}