Formal:
* Welkom op onze website. (This is the most common and neutral translation.)
* Van harte welkom op onze website. (This is a more emphatic and friendly welcome.)
Informal:
* Welkom op de website!
* Leuk dat je er bent! (This translates to "Nice that you're here!")
You can also use a specific greeting depending on the time of day:
* Goedemorgen! Welkom op onze website. (Good morning!)
* Goedemiddag! Welkom op onze website. (Good afternoon!)
* Goedenavond! Welkom op onze website. (Good evening!)
The best way to choose the right translation depends on the tone you want to set for your website.