The Internet is a great tool for measuring satisfaction, as the process for surveying customers can be automated, saving resources and money. However, it's only useful if the customers on your internet site are the same as those in the real world. If they are different, you'll need to run two satisfaction surveys, one for your Internet users and another for your real world customers.
There are a number of online web-based tools you can use to create a survey. Most don't even require coding skills. Here is an example of an online survey built using Surveymonkey.
You can place your survey either as a link on your page, as a pop-up, or just send it in an email. You should make sure that the survey isn't intrusive and appears after the user has used your service. You should also make sure that you don't present one survey repeatedly to the same users.
Any survey run on the Internet must obey data protection laws; so to make life easier, don't capture personally identifiable data, such as postcodes, etc.