Disabling browser's back functionality on sign out from Asp.Net

body {
	margin-left: 0px;
	margin-top: 0px;
	margin-right: 0px;
	margin-bottom: 0px;
}
.style7 
{
	font-family: Arial, Helvetica, sans-serif; 
	font-size: 12px; 
	font-weight: bold; 
	color: #0051a5; 
}

.style8 
{
	font-family: Arial, Helvetica, sans-serif;
	font-size: 12px;
	color: #FFFFFF;
	font-weight: bold;
}
.style9 
{
	font-family: Arial, Helvetica, sans-serif;
	font-size: 12px;
	font-weight: bold;
	color: #FFFFFF;
	text-decoration: none;
}
.style10 
{
	font-family: Arial, Helvetica, sans-serif;
	font-size: 12px;
	font-weight: bold;
	color: Green;
	text-decoration: underline;
}
label
{
	font-family: Arial, Helvetica, sans-serif; 
	font-size: 12px; 
	color: Black 
}
.GridHeader
{
	background-color:#006699; 
	FONT-WEIGHT: bold;
    FONT-SIZE: 12px;
    COLOR: #FFFFFF;
    FONT-FAMILY: Arial, Helvetica, sans-serif;
    border-width: 1;
    border-color: black;
    Border-Style :solid;
}

.GridItems
{
	border-top: #666666 1px solid;
	border-color:#006699;  
	FONT-WEIGHT: normal;
    FONT-SIZE: 12px;
    COLOR: #000000;
    FONT-FAMILY: Arial, Helvetica, sans-serif;
	border-bottom: #666666 1px solid;
	vertical-align:super;
	border-width: 1;
    border-color: black;
    Border-Style :solid ;
}

.GridAltItems
{
	border-top: #666666 1px solid;
	border-color:#006699;  
	FONT-WEIGHT: normal;
    FONT-SIZE: 12px;
    COLOR: #000000;
    FONT-FAMILY: Arial, Helvetica, sans-serif;
	border-bottom: #666666 1px solid;
	vertical-align:super;
	border-width: 1;
    border-color: black;
    Border-Style :solid ;
	background-color: #f9f9f9;
	
}
INPUT
{   
	BACKGROUND-COLOR: F0F8FF;
    BORDER-BOTTOM: #9e9e9e 1px solid;
    BORDER-LEFT: #9e9e9e 1px solid;
    BORDER-RIGHT: #9e9e9e 1px solid;
    BORDER-TOP: #9e9e9e 1px solid;
    font-family: Arial, Helvetica, sans-serif;
	font-size: 12px;
	color: black;
	text-decoration: none;
}

SELECT
{
    BACKGROUND-COLOR: F0F8FF;
    BORDER-BOTTOM: #9e9e9e 1px solid;
    BORDER-LEFT: #9e9e9e 1px solid;
    BORDER-RIGHT: #9e9e9e 1px solid;
    BORDER-TOP: #9e9e9e 1px solid;
    
    FONT-FAMILY: Arial, Verdana;
    FONT-SIZE: 8pt;
}

.ErrorMessage 
{
	font-family: Arial, Helvetica, sans-serif; 
	font-size: 12px; 
	font-weight: bold; 
	color:Red; 
}
.GridPaging
{
	font-size : 10pt;
	font-family:Verdana;
}