Google already offering Page Speed browser extensions for Firefox and Chrome to get suggestions to improve load of webpage, Google released/ made available Google Page Speed Online a Google labs project (no need to install browser extensions with this) runs diagnostics tests online for website and recommends things to done to speed up your website .
Page Speed Online provides same analysis as that of Page Speed browser extensions but uses different (Webkit-based) renderer and user agent.This online service offers Page Speed Mobile Analysis, fetches the contents on page with webkit renderer (same used on iPhone and Android devices) that emulates as a mobile device.
Since Page Speed Online checks mobile version of page, suggestions will be based on mobile devices and networks. Generally mobile devices are with less CPU power when compared to desktop hence you’ll get suggestion to reduce CPU consumption.
Visit Google Page Speed Online, enter your website URL and click “Analyze Performance” to get suggestions to speed up your website. These suggestions are tailored to optimizations for mobile sites.
Check Google Speed Online Faqs and Docs section for more details.