For Mac: Copy the file(Awesomium) from:
.../SteamApps/common/GarrysMod/Awesomium.Framework/Versions/Current/Awesomium And place it to:
.../SteamApps/common/GarrysMod/bin/Awesomium.
For Windows:
Windows users get bad coding seen as viruses
All you need to do is to add hl2 to your firewall whitelist
or to disable your firewall.