should a web app stay on a single page and why?

Question

I've just noticed that several web application such as gmail, google calendar, zoho writer, etc are implemented using a single page only (not counting the logging form, just the main application)

There's no "open link in new tab"(at least the app don't need to open any new page to be functional) and such. What are the reasons to implement it like that?

Answer 1

• Limit doing a whole page reload.
• Quicker response.

Answer 2

Number of pages is purely stylistic. Many modern web apps are single page. Many are multi page. It's upto you. However, there are more fundamental issues that you shouldn't neglect. One good resource that you might want to go through is Architecture of the World Wide Web.