logging.info()
logging.debug()
logging.error()

Add ?debug to URL's to see a pop-up debug console in AppEngine.

Quoted: To see logging information for your application, simply append '?debug' to the end of the URL. For example, if your application is running at http://helloworld.appspot.com/ you can view the debug console in real time by typing in http://helloworld.appspot.com/?debug. The debug console will appear in the lower right hand side of your app, as shown here in a simple greeting card application:

And the stable version of Firebug for Firefox is here - version 1.05

Instructions here on adding Firefox symbols to Visual Studio so I can debug the crashes I'm seeing in Firefox. I'm not running a checked build (not sure where to get those).

The latest crash backtrace is:

nsTextFrame::ClearTextRun(void)

> xul.dll!UnhookTextRunFromFrames(gfxTextRun * aTextRun=0x0d37c310) Line 325 C++
xul.dll!FrameTextRunCache::NotifyExpired(gfxTextRun * aTextRun=0x0d37c310) Line 373 C++
xul.dll!nsExpirationTracker<gfxTextRun,3>::AgeOneGeneration() Line 211 C++
xul.dll!nsExpirationTracker<gfxTextRun,3>::TimerCallback(nsITimer * aTimer=0x02e3e8b0, void * aThis=0x037c2d60) Line 301 C++
xul.dll!nsTimerImpl::Fire() Line 400 + 0x7 bytes C++
xul.dll!nsTimerEvent::Run() Line 492 C++
xul.dll!nsThread::ProcessNextEvent(int mayWait=1, int * result=0x0020f820) Line 511 C++
xul.dll!nsBaseAppShell::Run() Line 169 C++
xul.dll!nsAppStartup::Run() Line 182 C++
xul.dll!XRE_main(int argc=, char * * argv=, const nsXREAppData * aAppData=) Line 3174 C++
mozcrt19.dll!arena_malloc_small(arena_s * arena=0x00020040, unsigned int size=0, int zero=0) Line 3654 C
mozcrt19.dll!arena_malloc(arena_s * arena=0x00000000, unsigned int size=0, int zero=0) Line 3713 + 0x7 bytes C
mozcrt19.dll!malloc(unsigned int size=8491528) Line 5750 + 0x27 bytes C
xul.dll!nsLocalFile::Release() Line 753 + 0x13 bytes C++
xul.dll!nsRefPtr<nsIDOMEventListener>::~nsRefPtr<nsIDOMEventListener>() Line 957 C++
xul.dll!XRE_CreateAppData(nsILocalFile * aINIFile=0x00000001, nsXREAppData * * aAppData=0x008240a0) Line 139 C++
firefox.exe!wmain(int argc=1, wchar_t * * argv=0x00836080) Line 87 + 0xe6 bytes C++
firefox.exe!__tmainCRTStartup() Line 591 + 0x19 bytes C
kernel32.dll!77614911()
[Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll]
ntdll.dll!77a4e4b6()
ntdll.dll!77a4e489()

Dowload the symbol files needed to debug WIndows (all versions here - XP SP2, Server 2003, x64, ...).

Quoted: Provides information about download symbols.