il quella maniera non funziona molto bene.
avrei quasi risolto cosi.

css:

#
codice:
boxlogin { width:160px;  margin:0em auto;text-align:left }
#boxlogin1 { width:160px;  margin:0em auto; text-align:center }

#boxlogin { 
              
              margin:0; padding:0 0em; 
              border:1px solid #ccc; 
	 background:#E0DFE3 ; 
	 text-decoration:none; 
              height:1em;line-height:1em;
		} 
		
#boxlogin1 { 
        
        
              margin:0; padding:0 0em; 
              border:1px solid #ccc; 
	 background:#FAFAFD ; 
	 text-decoration:none; 
              height:1em;line-height:1em;
		}
html:

codice:
<div id="boxlogin"><h2>Area riservata</h2></div>
<div id="boxlogin1">
<form name="Sample" method="post" action="<? print $resultpage ?>">
 <span style="display:block">Username</span>
  <input style="display:block" type="text" name="username" size="12" maxlength="15">
 <span style="display:block">Password</span>
 <input style="display:block" type="password" name="password" size="12" maxlength="15">
 <input style="display:block" type="submit" name="Login" value="Login">
  </form>
  </div>
mi va bene per IE ma con moz mi si accavalla tutto il form