Hi GuiB,
I tried using your script replacing the three websites the original poster requested with the two websites I would like Firefox to open at the same time in one window (in two separate tabs). I am a complete newbie to applescript, so I do not completely understand what it is doing yet, however, it is successfully opening the two websites I want it to open in two separate tabs. However, there is an unwanted behavior of it opening a second blank firefox window in addition to the two tabs. So, I am wondering if there is a way to modify the script so that it does not open the extra firefox window. I'm wondering if this is happening because the original script was for three websites and I only need two? Thanks for reading and for your consideration. Here is the script I am running, based on the one you wrote.
Thanks,
Chris
set urlList to {"https://voice.google.com", "https://riot.im/app/"}
tell application "Firefox"
activate
repeat 40 times -- gives about 4 seconds to open Firefox if not opened
if frontmost then exit repeat
delay 0.1
end repeat
tell application "System Events" to tell application process "Firefox"
set oldNbrOfWindow to (count of windows)
keystroke "n" using command down
repeat 20 times
if ((count of windows) > oldNbrOfWindow) then exit repeat
delay 0.1
end repeat
end tell
repeat with the_url in urlList
open location the_url
end repeat
-- close the first default tab
tell application "System Events"
keystroke tab using control down
delay 0.2
keystroke "w" using command down
end tell
end tell