On Ubuntu Linux, you can build a bleeding-edge, development version of Firefox using the commands below.
Building Firefox requires at least 500MB of disk space free, at least 500MB of RAM, and lots of available swap space.
# Get the tools sudo apt-get build-dep firefox sudo apt-get install mercurial libasound2-dev libcurl4-openssl-dev # Get the source hg clone -r default http://hg.mozilla.org/mozilla-central/ cd mozilla-central # Configure autoconf-2.13 mkdir objdir-ff-release cd objdir-ff-release ../configure --enable-application=firefox # Build make -j4
However, this is not necessarily the best approach if you want to work on Mozilla. See the build documentation for the full story.