I’ve seen in the docs that I can communicate from my website with the unity app by sending messages:

SendMessage('MyGameObject', 'MyFunction', 'MyValue');  
but how can I send multiple values down to the function of that object using only one SendMessage?

Maybe that function needs several values…

Or can I pass some object and parse it with C#?
Thank you
              
So as it does not seem to be possible to send anything else than numbers and strings. The solution I came up with for now is sending a string with JS and then parsing it inside C#:
In Javascript Browser Code:
gameInstance.SendMessage(
    'Cylinder', 'HandleRotationString', '10|0|30'
In C# Unity Code:
void HandleRotationString(string coordinates) {
    string[] coord = coordinates.Split('|');
    float x = float.Parse(coord[0]);
    float y = float.Parse(coord[1]);
    float z = float.Parse(coord[2]);
    // ... use variables
I hope it helps someone.