Single key shortcuts in Opera 10 and previous versions remain a fascinating but uncovered feature. No keyboard combinations, a single key is just enough. Single key shortcuts were part and parcel of Opera 9.2 and previous versions but are disabled in Opera 9.5 and higher version. To enable them launch Opera browser and check the box marked “Enable single-key shortcuts” in Tools -> Preferences -> Advanced -> Shortcuts. Single Key Shortcuts are extra function keys and do not replace traditional multiple keyboard shortcuts.
Once enabled you can simply hit key ‘7’ for example to zoom out by 100% and ‘8’ to zoom in by 100% or ‘X’ for forward and ‘Z’ for backward. I find particularly interesting ‘S’ and ‘W’ to move forward and backwards through headings in page, ‘A’ and ‘Q’ to move back and forth through links in a page. Its very cool on well structured web sites like cnn.com
The experimental Firefox add-on aptly called “Single Key Tab Switch” brings the Opera-type-of single-key tab switching to Firefox. By default it lets you use keys ‘1’ and ‘2’ to go to previous and next tab, respectively – just like in Opera. This add-on does not replace Firefox’s traditional keyboard shortcuts for tab switching. Key bindings can be modified in about:config by editing these two properties; extensions.skts.prevTabKey and extensions.skts.nextTabKey.
Single Key Tab Switch extension works on Firefox 3.0 and higher version. Its a free download for all platforms with Firefox.
Follow-up: Complete list of Opera Single-key shortcuts