How to change/customize mail signature in Mountain Lion?

• open Mail
• create a new signature
• open this folder /Users/you/Library/Mail/V2/MailData/Signatures/
• open the latest *.mailsignature file with a text editor
• replace everything under this code with your custom html (replace iso-8859-1 with uft-8for umlaut support)

Content-Transfer-Encoding: quoted-printable
Content-Type: text/html;
    charset=iso-8859-1
Message-Id: <DDFB0C4D-5555-475C-9B54-115039EF5FE0@Speedport_W_722V_Typ_B>
Mime-Version: 1.0 (Mac OS X Mail 6.0 \(1486\))

• save the file and open the Get Info Dialogue and check Locked, so that it doesn't get overwritten by Mail

Objective-C string replace

NSString *testStr = @"This is a test work.";
    
testStr = [testStr stringByReplacingOccurrencesOfString:@"work" withString:@"word"];