Add-on-Con Is there a good reason to build a browser add-on for Internet Explorer as well as Firefox? Yes, according to Microsoft IE evangelist Joshua Allen. Building an add-on for IE is so difficult, he said, your browser app competitors won't even bother.

"It's harder to write apps for IE - so it's a harder market for competitors to get into," Allen told developers this morning at Add-on-Con, a Mountain View, California, mini-conference dedicated to, yes, building browser add-ons.

Of course, Allen also argued that IE has more market share. "You want to get to that 70 per cent of the market that uses Internet Explorer," he said. "Right now, IE 6 probably has more market share than Firefox."

And he pointed out that Firefox users are more likely to "mess" with your business model. "They tend to install things like ad blockers, whereas the Internet Explorer user is more mainstream."

Allen acknowledged that add-on makers are more likely to launch their tools on Firefox, a platform that offers real developer tools. He even said that launching on Firefox is the way to go because Michael "TechCrunch" Arrington is more likely to review your product. Arrington - blogging's king maker to start ups - is a Mac man, and Macs don't run IE.

But Allen is happy to say IE 8 will solve the developer tools problem. And he insisted that although porting add-ons to IE is annoying, it can be done. "With Firefox, you've got this more enthusiast audience, more of a controlled test bed. It's a good place to try out ideas before porting them to Internet Explorer," he said.

If you port your Firefox add-on to IE, you may have to use C++. And Allen admitted that this is a bit 1998. "The first thing people say is 'That's horrible. No one programs in C++ anymore,'" he said. But he reckoned there are ways of using languages like Python or Microsoft's C#.

This involves using the .NET Common Language Runtime (CLR). But the trick here is that you'll have to make sure your add-on works on all versions of the CLR. Microsoft only loads one version of the CLR for each IE executable, so you have to make sure there are no breaking changes between versions. "It's a little bit tricky," Allen said.

But go ahead. Give it a shot. Yours competitors won't. ®