>Can all zone (Zone 1-6) travel card for 3 day be used for all tube and bus journeys (bus jorney at airport hotel to tube station nearby)?<

Yes, the travelcard is good for all tube and bus trips, as long as the bus is one of the regular London buses.

There is a 3 day London Visitor Travelcard which must be purchased prior to visiting London. You can have it delivered or you can pick it up in London. It works in Zones 1-6 and is good on the following:

London Underground
London Buses
National Rail Trains
The Docklands Light Railway
Tramlink

Cost is 19.20 GBP. Information on purchasing is available here:

http://www.londontravelpass.com/index.asp

If you want to purchase a 3 day Travelcard once you get to London, you can buy one at any tube station. A Zone 1-6 TC will cost 36 GBP for peak times (travel anytime during the day) or 18 GBP for off peak (travel after 9:30 am Mon to Fri). Info is here:

http://www.tfl.gov.uk/tfl/fares-tick...rd-day-2.shtml

What is the difference between 18/36GBP 3 day travel card i can buy when in LONDON and 19.20 GBP 3 day travel card i can buy online http://www.londontravelpass.com/index.asp from outside london? is there any difference in both cards as to the way i can use buses/tubes (time limit or any other difference)?

isn't it good idea to go for 18GBP offpeak hour travel card when in london then pay 19.2GBP overseas?

Also in non-peak card which hours I can't travel?

The London Visitor Travelcard (19.20 GBP) is only available to overseas visitors, thus the requirement that you purchase it prior to your trip. The 3 Day Travelcard (peak or off peak) can be purchased by anyone at any tube station in London.

The off peak travelcard (18 GBP) can't be used prior to 9:30 am Monday to Friday. That won't work well for you since you are staying near the airport. You won't get into central London until 10:30 or 11:00 am. If it were me, I'd spend only a little more for the Visitor Travelcard and have no time restrictions.

Both cards will give you access to the same modes of transporation.

The London Visitor Travelcard (19.20 GBP) as per website says if its 3 day card then no travel restrictions (peak/non-peak) which means for visitors its 19.2GBP for 3 day peak hour usage instead of 36GBP locally. May be its to promote tourism.

Also site says The London Visitor Travelcard can be used on Trains, DLR and TRAM too, and i believe 3 day 18/36GBP local card can be used only in Tube and Buses.

>Also site says The London Visitor Travelcard can be used on Trains, DLR and TRAM too, and i believe 3 day 18/36GBP local card can be used only in Tube and Buses.<

Please read the site more closely. Both travelcards are good on the same modes of transport.

The value of the London Visitor Travelcard for 3 days in Zones 1-6 is a bargain. The vast majority of visitors stay and travel in Zones 1&2 and their costs for a 3 day Travelcard would be much less than a person like you staying and commuting from Zone 6.