Exit Steam completely
Open Task Manager and end any Steam-related processes
Press Win + R
Type `%localappdata%Steamhtmlcache` and press Enter
Delete all files and folders inside `htmlcache`
Press Win + R
Type `%appdata%Steam` and press Enter
Delete the `appcache` folder if present
Press Win + R
Type `C:Program Files (x86)Steam` or your Steam install folder and press Enter
Delete the `appcache` folder if present
Restart Steam