iPhone web apps or iPhone web 2.0 applications were introduced with the release of the initial iPhone 2G in June 2007. At that time, it wasn't possible to install applications on the iPhone. The App Store was not available yet and there was no way for iPhone owners to install applications on the device. It was a closed system.
Apple introduced iPhone web 2.0 applications support, and the ability to run applications using Mobile iPhone Safari as a quick solution until the release of the SDK (System Development Kit). Later in 2008, the SDK was released, and combined with the App Store, iPhone owners were able to install native applications on their iPhones.
Theoretically, web apps should run on any internet browser. However, iPhone webapps will not render correctly on a desktop browser, and will require an iPhone Safari or any iPhone web browser and any iPhone or iPhone 4 to run.
How to run an iPhone web app:
iPhone Web applications use Mobile Safari or any iPhone web browser to run by entering the web app URL address. There are two types of iPhone web applications on the iPhone in terms of workability. One type of web 2.0 iPhone apps run inside the safari browser, while the other type run independent of Safari.
iPhone webapps that run inside Safari:
Most iPhone web applications start inside the Safari browser window. You can tell by recognizing the Safari address and the google search bars within the web app and as you slide your finger up or down. The whole iPhone browser window will move. The window is not fixed.
Those type of Web apps make great sense for some iPhone applications that need to pull information from the internet constantly. Those iPhone applications need internet connection anyway even if you download the apps from the app store.
Web applications like news, translators, maps, weather and social network are OK to run inside a web browser as you will get the information you want. They are also good for simple games like Chess, Sudoku and others.
To quit a web app running in an iPhone Safari window, simply tap the x button to close it just like closing any web page from any iPhone browser.
With this type of iPhone webapps you can add the web app as a bookmark simply by tapping the plus button and add it to your favorite just like any other iPhone Safari bookmark. You can also add it to the home screen.
iPhone webapps that run independent of Safari:
Some iPhone and iPhone 4 web applications will ask you to add the web clip icon, which is an iPhone icon to your Home Screen once you start it in Safari. This happens with some newer web 2.0 iPhone apps and mostly with games.
Simply tap the plus button to add the web clip to the home screen as requested, and then tap the icon from the home screen to start the web app.
Those iphone third party web apps that require an iPhone icon to be installed on the home screen will run independently of Mobile Safari afterwards. For example, the web apps shown below don't use the Safari interface. This is specially true with Web 2.0 iPhone games.
Most iPhone web applications require internet connection to start as they are not stored in the iPhone. Those webapps run from a server on the internet, and therefore, you have to have an internet connection to retrieve the data.
Web 2.0 apps have improved dramatically, that some web apps require internet connection only initially to install, but after they are installed, no Internet connection is required.
Pie Guy is such an example of such iPhone web application. It installs directly to the iPhone by passing the Apple approval process, and will run without the need of an internet connection.
Simple web apps are nice, but of course you shouldn't expect much from them. You shouldn't expect web apps to take over native iPhone applications or the App Store. It is just not possible at this time. Maybe in the future.
Advantages of iPhone web applications:
No need to submit to apple for approval or pay any fees
Universal, and can be available for any web browser on any platform which means bigger market for developers.
To update a web app, all what the developer has to do is update the code on the server. You are always guaranteed to run the latest updated web app on your device.
Since the web app is running from a server, you save space on your iPhone.
Disadvantages of iPhone web applications:
No simple way of making a payment for a web app compared to the easy click and pay of the App Store.
No true full screen mode. Notice the status bar in all those iPhone web applications. It can't simply be removed as shown in the picture. This can be annoying with games .
Most Web apps require internet connection, however, some modern web 2.0 iPhone apps can be installed locally on the iPhone as seen with Pie Guy web app. It required no internet access after installation.
The majority of iPhone web applications require a connection to the internet. This simply means that iPod Touch owners are out and it also means lower market for the developer.
No sound support with web apps as of now.
iPhone web applications are slower than native apps, and less capable.
Lose the uniqueness of the device. The Apple iPhone is a unique phone, with a unique iOS operating system and a unique App Store. Running web Apps will make it look like any other Smart phone running the same web app.