The recent snow was quite severe in my area, and at various points the phone line we use for our internet connection went down.

An additional relevant factor is that the mobile signal is not strong enough to receive data via a dongle.

I think every trader should have a set of rules to cover loss of internet connection, both for new trades and existing trades.

I have an incredibly simple set of rules, which form part of the contingency plan section of my 2010 -2011 trading business plan (an 82 page document).

The rules say I cant trade if there is no internet connection: no new trades, and exit all existing positions.

So that is what I did, and had to wait several days for the line to be repaired.

You might consider that quite a drastic step, and you might have rules that say that no new trades, but keep existing ones with a stop and limit order to exit, for instance. The point is not so much what the rules are but rather that this particular contingency has been thought about in advance, and the rules are documented.