A new toolkit aims to kickstart the development of Facebook iFrame applications, which enable users to add custom tabs on Facebook fan pages, based on a similar toolkit for Twitter.

An iFrame app allows the user to embed an external Web page in their custom Facebook page tab.

The user’s “index” or “canvas” is actually hosted on a non-Facebook server and is surrounded by Facebook “chrome”, which are the Facebook elements on the page.

Because the “iFramed” page isn’t hosted on Facebook, it can use standard HTML, CSS and JavaScript like any other Web page does.

Fbootstrapp, created by Clemens Krack, is a toolkit for kick-starting the development of Facebook iFrame apps. It is based on Bootstrap, which is a GUI toolkit for Twitter.

“I just pushed my last version of Fbootstrapp. It’s a fork of Twitter’s Bootstrap, which aims to help developing Facebook iFrame apps,” Krack said in a blog.

“The default grid systems provided as part of Fbootstrapp are a 760px and a 520px wide 12-column grids.”

“They are a flavour of the popular 960 grid system, but without the additional margin/padding on the left and right sides.”

As with Bootstrap, Fbootstrapp includes base CSS and HTML for topography, forms, buttons, tables, grids, navigation, alerts, etc. It also shares Facebook’s look and feel.

“As some researchers found out, it is more intuitive for users to style elements within apps and fan pages in the same look as the parenting Facebook site,” Krack said on the Fbootstrapp site.

Using Fbootstrapp, Krack said developers can now “go and build awesome apps for Facebook”.

Last week, StartupSmart reported on the impending launch of Apptopia, a marketplace designed to help broker the sale of mobile apps, providing an exit strategy for developers.

Founded by Eliran Sapir and Jonathan Kay, Apptopia will launch in February. It has already secured seed funding, including $110,000 from Expansion VC.

“Apptopia is the marketplace that will broker the sale of [mobile] apps,” the founders say on their website.

“We will manage the entire process through to completion, starting with recommending app valuation and connecting sellers [and] concluding with escrow services, code review, and interfacing with Apple and Google.”

Apptopia has already brokered the sale of one mobile app valued at more than $15,000, and has 30 more lined up for February’s launch.

To kick off its launch, the first 200 developers who sign up will not have to pay the listing fee.