I have Visual Studio 2013 (tested with Update 1, 2 and 3) installed on two completely seperate machines, one is Windows 7 SP1 and one is Windows 8.1. Both are running the latest version of Firefox and Firefox is set to be the default browser. The Firefox setting "Open tab instead of new window" is checked.
Almost every time I want to open the API help pages on MSDN by pressing F1 in the code, a new Firefox window is opened. This happens on both machines. But it only happens with Firefox, when IE is the default browser it correctly opens a new tab. And this is a new problem in Visual Studio 2013, I didn't have this problem with Visual Studio 2010.
Interestingly, this is not 100% consistent. Rarely, I'd say about 5% of the time, it correctly opens a new tab instead of a new window. And I have found one command that always correctly opens a tab, that is the Help - View Help command in the main menu bar (not very helpful).
Searching the internet revealed this Microsoft Connect issue entry which says that it was also a problem in Visual Studio 2012, but was apparently fixed in the latest build in May 2013. While I've never used Visual Studio 2012 myself, this date was before Visual Studio 2013 was released, and was far before Update 1 for it was released. Did they really forget to merge the fix to Visual Studio 2013?
Anyway, my question is if everyone experiences this problem and if not, if anyone knows a way to fix it.
Update with workaround
I've no idea how or why this works, but I've found a workaround. As long as the .NET Reflector (I'm using version 126.96.36.199) is running, the F1 key works correctly. This is 100% reproduceable and works on Windows 7 and Windows 8.1.
Can someone please explain that to me?
I'll leave this question open until a real answer is found.
Visual Studio 2015 shows the same problem.