update FAQ from main branch

FAQ

@@ -28,6 +28,7 @@ OpenSSL  -  Frequently Asked Questions
 * How can I remove the passphrase on a private key?
 * Why can't I use OpenSSL certificates with SSL client authentication?
 * Why does my browser give a warning about a mismatched hostname?
+* How do I install a CA certificate into a browser?
 
 [BUILD] Questions about building and testing OpenSSL
 
@@ -323,6 +324,26 @@ Browsers expect the server's hostname to match the value in the commonName
 (CN) field of the certificate. If it does not then you get a warning.
 
 
+* How do I install a CA certificate into a browser?
+
+The usual way is to send the DER encoded certificate to the browser as
+MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
+link. On MSIE certain extensions such as .der or .cacert may also work, or you
+can import the certificate using the certificate import wizard.
+
+You can convert a certificate to DER form using the command:
+
+openssl x509 -in ca.pem -outform DER -out ca.der
+
+Occasionally someone suggests using a command such as:
+
+openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
+
+DO NOT DO THIS! This command will give away your CAs private key and
+reduces its security to zero: allowing anyone to forge certificates in
+whatever name they choose.
+
+
 [BUILD] =======================================================================
 
 * Why does the linker complain about undefined symbols?