update any theme any version Rated 5 out of 5 stars
download your theme. Don't worry about "...don't support mozilla xx" Download it and save in a folder with "save link as" and then you have got the jar file. Open it with winrar, 7zip...look for the install.rdf file and extract it. change the line like this "<em:maxVersion>17.*</em:maxVersion>. Close the file. If you see that appears another install.rdf file in the jar file delte it. Now, only left click and move your new install.rdf into the .jar file. End installing it like a thunderbird extension (install from folder) if you have any question feel free to ask me once again.