Signature is the block of text that gives some brief information like your name, your phone number, your email address, your company or organization or business or university or college or school name and any other details like any url and quotations you want to include as an author or the owner of the email message. In Wikipedia it is quoted as
A signature block (often abbreviated as signature, sig block, sig file, .sig, dot sig, siggy, or just sig) is a block of text automatically appended at the bottom of an e-mail message, Usenet article, or forum post. This has the effect of “signing off” the message and in a reply message of indicating that no more response follows. It is common practice for a signature block to consist of one or more lines containing some brief information on the author of the message.
1. Go to Settings at the top right corner of your Gmail page
2. In the General tab of the Settings, find out the Signature setting. Remove the selection from No Signature by selection the second radio button:-
4. To check whether the changes are saved, go to and click Compose Mail link at the top left of the Gmail Page
You would see the compose message window as below:-
So, have a Signature sent with your mail that would represent you as an identity.
You can remove the two – i.e. — appearing before the quoted text in the Signature…read this for more details
You can also append your Location to your Signature…read this for more details
You can create Random Signatures with different quotations each time…read this for more details
Currently, you cannot attach images like .gif file for your Signature in Gmail. Hope this feature comes soon.
The outgoing mails can be either single mails, or can be reply to some mail or can be a forwarded mail. In fact the mail that you are sending can have a chain of quoted text i.e. chain of mails that you are replying to or forwarding it to someone, as you have to keep the originally quoted text reference.
So the above default Signature appending method of Gmail would append the signature at the bottom of the chain of the mails expecting you to write your message at the bottom of the chain and then send it. This is called Bottom Posting. But some people would like to send the chains in reverse order like, the latest on the top, called Top Posting. In this case, you would need that the Gmail Signature should be appended at the top of all the messages, if not, you would have to cut paste the appended Signature from the bottom to the top. There is a provision in Gmail to append the Signature at the top of the chain of mails with quoted texts.
You can read about top and bottom posting for mails and which is the best one in detail here