WebP is an image format that employs both lossy and lossless compression. The degree of compression is adjustable so a user can choose the trade-off between file size and image quality. WebP typically achieves an average of 39% more compression than JPEG and JPEG 2000, without loss of image quality.
But a few browsers support WebP right now (as of April 2010, Google Chrome 9+ and Opera 11.10 beta), how to use it?
Now you can use webptest to test browser whether it supports.