Hi Hervert,
I downloaded the installer, 64bit .rpm, and installed it with yum on Fedora 20 64bit.
Then launched google-webdesigner from the terminal and started fine, although there was a message.
[ume@localhost ~]$ google-webdesigner
which: no opera in (/usr/lib64/qt-3.3/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/home/ume/.local/bin:/home/ume/bin)
ATTENTION: default value of option force_s3tc_enable overridden by environment.
I also checked libXtst. My Fedora is pretty much vanilla (for testing) and I just applied yum update to the clean installed system.
[ume@localhost ~]$ sudo updatedb
[sudo] password for ume:
[ume@localhost ~]$ locate libXtst
/usr/lib64/libXtst.so.6
/usr/lib64/libXtst.so.6.1.0
/usr/share/doc/libXtst
/usr/share/doc/libXtst/COPYING
I'm wondering if you can try installing libXtst?
Thanks,
Ume
(GWD team)