Is it legal to sell LV handbags online
If they are replicas, then yes. If they are counterfeit, then no.
with a disclaimer stating that they are immitations of the real thing.
Oh, so you want to sell counterfeits, not replicas. Then no, it is not legal, and the disclaimer will not protect you.
I see a lot of website do so.
Lots of people exceed the speed limit -- but that's no excuse if you are the one that gets caught doing it.
Generally, replica bags are okay -- bags that have the same general styling as an LV bag, for example. But if you use fabric that has the LV logo, or any part of the bag has an LV logo (or an LU logo that looks like an LV until you stare at it), or you use the term "LV" anywhere in your advertising, then you are violating trademark laws, and could get in a whole heap of trouble.