From time to time I have to reset my modem , reason I lost the internet connection .
Googling I find that a lot of people meet the same problem.
But I never find the reason why it lost the internet connection.
As a example in my case if go in the menu of modem router ,
it shows the connection to my other PC being a MAC it shows me my Apple TV
the wireless connection of the Apple TV including the name of the wireless
connection.
But again no internet on both PC.
Yes I know to solve reset the modem router .
But again why ?

I have had problems like this also. Tured out to be mu ISP and problems they have.

I would suggest you call your ISP and open a trouble ticket if you want to try and track down the cause.

If you talk about ADSL or any cable modems, you definitely need to ask your ISP, and I suggest to write down the time when you lose connection to tell them.

ADSL providers like to change IP ones a day, for that purpose they disconnect all clients modem from their access mux (or something like that). After that your modem is supposed to reconnect and get new IP. May be something goes wrong.

Yes I call my Provider and every time the answer is every thing on this side is ok.
Yes it is a adsl connection on standard telephone line .
They try to tell me that was because I use linux and MAC Snow leopard.
They said we do not support linux an MAC OSX.
I told them that it has nothing to do with the OS they do not believe me.
No when I sign up they promise that I get a fixed IP adress

Log into your ADSL modem and check its system log.

If it doesn't logging just enable it. They simply give you the same IP, but they have to disconnect ones per day.

Bad ISP: You are correct.

They always say that. Six months(?) ago I had DSL signal, but no connectivity. I was put through to my ISPs call centre in India. "Everything OK here, problem is at your end. We don't support linux, please use Internet Explorer 6.0 or better ...."

12Hrs later it turns out most of London is disconnected because someone has dug through a deeply buried and massive fibre-optic cable. Three days later, service was resumed.

Meanwhile, some options for you to try:

- Check your Modem / router's config pages (usually with http://IP.OF.MODEM.ROUTER) and see if there is an option to "Automatically reconnect if there is a disconnection". If so, please try enabling it.

- Get yourself (or borrow) another DSL modem / router which has that option.

- Change your ISP. Perhaps they are rubbish (some are).

Your "Location:" is listed as "In front of my LINUX OR MAC BOX", and whilst this might be (mildly) amusing at first read, it doesn't help those of us with location-specific knowledge to help you. And your ISP is? - Again, it might be relevant to your problem.