LiveHTTPHeaders and Firefox 2.0

As other people have already noted, the LiveHTTPHeaders Mozilla extension does not work on Firefox 2.0 (yet), since it has not been marked compatible with the new version yet. However there are two ways in which you can "force" Firefox 2.0 to activate the extension. Both are of course to be considered as hacks until a new version of the extension is released.
The first way is to change the extension itself. Download the XPI package and unzip it (yes, it's a ZIP file; if you are using a GUI tool you may want to change the file extension to .zip first). The contents of the package will look like this:



Open the install.rdf file (it's XML). There you will find the following XML element (around line 16):

<em:maxVersion>1.5+</em:maxVersion>

Change the maximum version number to 2.0+, zip all files, provide an .xpi file extension, and you are ready to install the extension.

The second way is easier yet potentially more dangerous: Just tell Firefox to install extensions regardless of the minimum/maximum required version numbers they supply in the install.rdf file. In order to do so, call the special URL about:config in Firefox and create a new boolean setting called extensions.checkCompatibility with a value of false. This then obviously applies to all extensions.
Of course the best way is to wait till a new LiveHTTPHeaders version for Firefox 2.0 has been released, since there is no guarantee that the current version (0.12) is fully compatible with the new browser version. However on one of my test systems it seems to run quite nicely (using the first workaround from this entry).