Auto Responding Chat Box for my website.

I am building my website on [login to view URL] and I am in need of a plain chat box that AUTO REPLIES to each individual that visits my website and acts as live support. As soon as someone clicks my link they will only see a big chat box and a message from my auto reply. A script of about 20-30 lines will need to be added to the chat box but only replies to my customer after they click send or enter, bc I dont need the script to be spit all out at once. Also keywords will be needed to be inserted and changed at any given time along with the script , font size, color and font style of the responses our chat box sends. Please be familiar with coding for a website bc this will need to be embedded into my website. i attached a screen shot as an example of what I need for my website, however there is a section in red that I "X" out thats not needed and the background doesnt have to be a pic I'd rather it be a solid color. But I also need to make sure that the chat box starts the convo and auto replies back to my customers after they type and send their message back to the chat box..along with a keyword system.. I also have a yola account t hat I will give you the user name and password to so you can create it on that format to make things very easy.