Have you ever sent an email and then immediately regretted sending it? If you are using Gmail as your mail client, you can do just that with an interesting but buried option in Gmail settings.

To enable this feature, go to Mail Settings in Gmail (upper right corner, under the gear icon). Navigate to the "Labs" tab. In the labs search box, look for "Undo Send" and choose Enable, then save. Now in Mail Settings you will see an option to "Undo Send: Send cancellation period: __ seconds." Enter the number of seconds that Gmail will allow you to change your mind in the future (try 10 seconds).

With this enabled, the next time you send an email, you’ll be able to “Cancel” it from being sent out, as long as it is within the time frame you specified.

Do you prefer Bing over Google but like Google's sparse but fast loading page better? With this tip you can get the best of both worlds.

As users of Bing know, when you visit the home page of Bing, a page with a featured photo as the background is displayed by default, which increases the load time of the page. This can be distracting or annoying—especially if you have a slow connection. Disable this photo from loading by simply bookmarking this URL (http://www.bing.com/?rb=0). The next time you visit Bing, the photo will not appear.

Did you know that on iOS5 on the iPad, you can actually split the keyboard into two? This can be useful for typing with your thumbs if you are holding the iPad with both hands.

To do so, press and hold the keyboard icon on the on-screen keyboard. An option will appear, allowing you to split the keyboard into two. Alternatively you can drag the keyboard icon up across the screen until the keyboard splits up. Still another way is to simply put two fingers around the center of the keyboard and simultaneously drag them apart in a splitting motion.

Want to do a quick currency conversion? You can use Google for that. Simply type in the amount in the original currency, then the currency you want to convert it to.

For example, type in: "100 dollars in yen" or "100 dollars in Mexican Pesos" and check out the results. If you have a mobile data plan on your mobile phone with a browser, you can use this tip for quick currency conversions on the go.

The Mac introduced the concept of using multiple "Desktops" (previously called "Spaces") using Lion's Mission Control application. Using Mission Control, you can specify which desktop applications will automatically open in which desktops by default.

To set your preferences, select and right-click (or ctrl+click or two-finger click) on an application in the Dock, then select the "Options" menu in the resulting pop-over. Inside that menu, links appear that allow you to remove the app from the Dock, open it at Login, or to have it Show in the Finder app. If you have multiple desktops active, an additional set of options will appear at the bottom. Here you can "assign" the app to "This Desktop" or the current active desktop, or to open in "All Desktops" or "None." Make your selection and your app will now open in the specific Desktop or Desktops you specify on launch.

If you use an iPad, there is a switch conveniently located at the right side of the device which you can set to either lock the orientation of the screen or to mute the audio when you slide the switch—depending on your preference.

To set your preference, go to Settings > General, and under the "Use Side Switch" section, choose either "Lock Rotation" or "Mute."

If you, for example, install multiple media player applications on your Android device, you’ll find that Android will give you the choice of which application to launch by default when you open a media file or document. However, you may later want to change this default setting.

To do so, go to Settings > Applications > Manage applications and then press the "All" tab. Choose the application that you previously selected as default, and scroll to the section "Launch by default" and press the "Clear defaults" button. Next time you open that particular type of file in the future, Android will prompt you again to choose a new default app.

Ever surfed for the number of a pizza place on your iPhone and just wanted to dial the phone number straight from the webpage? If you are using the default browser on your iPhone, which is Safari, that's no problem at all.

Safari automatically converts numbers that look like phone numbers into links. If you press those links, a popup window will appear giving you the option to call the number from there or cancel. No need to write down or even copy and paste the numbers.

If you are using Internet Explorer and Windows 7, you may have noticed that when you mouse over an IE browser window, a preview of the open tabs in the browser is shown. While this is useful to give you an idea of the sites you have open, it can get annoying if you have multiple tabs open at the same time. If you would prefer to disable this feature, you can.

Just go to Tools > Internet Options (in the upper right-hand corner of the browser) and then click on the "Settings" button in the window that pops up. In the list of Tabbed Browsing Settings, uncheck "Show previews for individual tabs in the taskbar." Click on OK and you should be good to go.

A very useful feature in Microsoft Office is called "AutoRecover", which automatically saves your document at specified time intervals so that in case of an application or system crash, Office can recover its latest version.

By default this is set to 10 minutes, but you can change this easily by clicking on the Office button within the application, and then clicking on the "Word Options" or "Excel Options" (or other application) button in the lower right hand side of the window. Go to the "Save" section and look for "Save AutoRecover information every…" and change the settings there. Be sure to click "OK" to save your preference. A word of caution: setting the interval at very short timespans such as every 1 minute can slow down your computer with frequent writes to the hard disk. Try a number between 5 minutes to 10 minutes first.