Thanks to Swaroop who pointed out why the image we posted on our last post showed up and why people now see Gmail loading even faster. An Offical post where Gmail team explained

We reduced the weight of each request itself by eliminating or narrowing the scope of some of our cookies. We made sure that all our images were cacheable by the browser, and we consolidated small icon images into single meta-images, a technique known as spriting. We combined several requests into a single combined request and response. The result is that it now takes as few as four requests from the click of the “Sign in” button to the display of your inbox.

That really sounds a good technique. Here is what Spriting means

Spriting is usually defined as the act of creating partially transparent 2d raster graphics for use in video games, commonly referred to as sprites; by extension, it is also used to refer to the act of creating pixel art, though not all sprites are necessarily done in that style. Pixel art comprises a large part of “sprite art” as a whole; though technological advances since the mid-nineties allowed pre-rendered raytraced imagery, or essentially any 2-dimensional image style to be used as a sprite. In some communities, “pixel art” is considered a synonym of “sprite art”, and classification of artwork as “sprite art” is held to the same standards.

Thanks Swaroop.