At last! The latest version of Google’s Chrome Web browser has added tab icons to notify you if a tab is playing audio, accessing your microphone, or being cast to a Google Chromecast. The new audio alert icon should make it easier to find and silence annoying autoplay videos, such as on sites like -cough- Macworld. The other interesting addition is a preview of the new supervised users mode (ideal for young children), which lets you see a user’s browsing history and restrict access on a per-site basis. follow link
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).
Google Chrome Simplifies Silencing Noisy Tabs