First you need the world's best,fastest, light weight and most secured browser - Firefox
Click banner on the left side bar on the page to download firefox
Then download this Firefox addon by clicking here. https://addons.mozilla.org/en-US/firefox/downloads/file/15710/better_gmail-0.6.1-fx.xpi
You will get a warning..
Just click the options button on that yellow bar and give add allow the site. Then it will install the addon.
Conversation preview, Signature float - enable HTML Signature the easiest way, Smart Read button, Customize GMail Sidebar, Skins !!!, Macros, Label Colors, Date Search and lot more....
Yes, all in one pack.
I loved the feature of GMail HTML Signature, its better than all the other methods available currently, because it prevents copy pasting each time. Its like GMail's built-in feature.
Go to Settings > Signature
Then go to Signature and enter some html code like shown in screenshot.
Then go to compose mail and see your html sign working
Another feature i loved is the conversation preview with right click.
Also the skins look pretty good.
Yes this is nothing but GMail with Better GMail addon... Click to see bigger screenshot.
Please post comments about doubts, or more of this kinda information