Hi Luka, There are many possibilities depending on your situation.  Firewalls, Browsers and other security issues make finding a single overriding solution almost impossible.  Are you trying to print from a standard cloud based server, or to a local network?  Do you want to manage printing from the server or more locally on browsers? How are the printers connected to the website (or PC/smartphone), via network, USB, Bluetooth, serial, etc?  Are your web customers primarily using PCs or are they mobile?  Are you only printing to Zebra printers?

The QLn320 has several ways of handling many of these options, but it depends on your situation. 

All of these are big factors in what type of solution will work best for your use case.  If you simply don't know, then the most universal option is to convert what you want to print into a PDF, and let the PDF renderers work with drivers/apps to print.  Your customers can also set up the QLn320 as a PDF printer (for a small fee) and they can send the PDF directly to it.  You might not get the print quality you want, nor do you have any control over printing, but it works on most systems and is usually easy.  I wouldn't recommend it for high throughput situations or where you need to be sure the printing occurred. 
Some other options:
Zebra Technologies - Zebra Web Printing Solutions

Robin West
Solution Architect