Google Tips for Signature Blocks and Undo Send
Google has graduated two lab functions to full service. This means that there are two new options in Google Mail Settings for all users...
1. If you hate how the signature block on your email always winds up all the way at the bottom of the email string in a conversation, you can now change it. In your Google Mail settings, look for "Signature". Under the signature block, you can check a box that says "Insert this signature before quoted text in replies and remove the "--" line that precedes it."
2. If you sometimes hit the send button prematurely, you can turn on "undo send". Again, it's in the Google Mail settings. Check the box for "undo send", and choose your preference regarding how long the Undo Send option is available. The longest duration available is 30 seconds.