Security Keys

i have installed wordpress 2.8.4 three weeks before . and now i want to update my security level so i have edited in
“define(‘AUTH_KEY’, ‘:dr+%/5V4sAUG-gg%aS*v;&xGhd%{YKC^Z7KKGh j>k[.Nf$y7iGKdJ3c*[Kr5Bg’);
define(‘SECURE_AUTH_KEY’, ‘TufWOuA _.t>#+hA?^|3RfGTm>@*+S=8\”\’+\”}]<m#+}V)p:Qi?jXLq,<h\\`39m_(‘);
define(‘LOGGED_IN_KEY’, ‘S~AACm4h1;T^\”qW3_8Zv!Ji=y|)~5i63JI |Al[(<YS<2V^$T])=8Xh2a:b:}U_E’);
define(‘NONCE_KEY’, ‘k1+EOc-&w?hG8j84>6L9v\”6C89NH?ui{*3\\(t09mumL/fFP_!K$JCEkLuy ={x{0’);”

if i updated my web page becoming white screen what i should do?????????????/

please help me out
thanks for reading my post