htttp and www both required for url search?

UK site doesn't appear without both in url

[temos]

In the US both our US and UK sites are available by typing in either www. or http// BUT a recent UK trip revealed both had to be entered or the site did not appear.
However sites such as msn.com work fine in the UK with either/ or www. /http
What gives?

[4eyes]

Not sure why this would happen, but then I'm not an expert on how domains are resolved, and all the sites on our UK based server can be viewed using either.

Possibly connected with the ISP used?

Any one got a better take on this?

[added]
maybe a browser autocomplete thing?

[IanTurner]

I am happily seeing my sites with either a [www....] or www. using IE.

I am sure that is not an issue with domains being resolved differently in the UK to the US.

As 4Eyes suggests I would look at browser preferences as being the most likely cause.

[DaveAtIFG]

A browser surfs to a site using an IP address. It does a DNS lookup in response to a user's input, then requests the page from the site by IP, so this is a question of how DNS names are resolved in your neighborhood. There's a recent discussion here [webmasterworld.com] that's related, but doesn't fully answer this question.