There are formulas for valuation businesses based on their revenue and/or profit. However these are specific to different types business.
I am not aware of any indepth study done on the valuation of web based businesses. For a website there are no real fixed assets. Of course there is value in the intellectual property of the web pages, configuration and any scripting. As well the goodwill a existing website has in attracting returning vistors and new vistors from search engines.
So based on similar advertising based small businesses. I would say the value would be 3 times the annual operating revenue.
Or 5 times the annual net profit. The is a real net profit, with person who is doing the work actually being paid a salary or wage. Some small businesses the owner does work but doesn't draw a salary so as to make the net profit look bigger than it really is.