At Eretz Hemdah, we have written extensively on these issues. See our reponsa, Bemareh Habazak vol. 5 siman 37-4 in the following link:
Below is a translation to English of part of the responses which appear in the link:
The amazing development of the virtual world – the Internet – in the past years, places a Halachic and spiritual challenge before the Rabbis. The Halachic rulers need to think of the many dangers on one hand, and of all of the advantages on the other.
In this answer there has been an attempt to combine old and new and to try and find the sources in Chazal and in the words of the Rishonim and Achronim for the new reality.
In leaving a Jewish-owned Internet site open on Shabbat and Yom Tov the questions that arise deal with several prohibitions:
a. "Lifney Iver" ('putting a stumbling block before the blind' – causing failure to someone else) and "Mesaye'ah Le'overy Aveira" (assisting a transgressor);
b. Sales on Shabbat (in commercial sites);
c. Shabbat salary (in sites which collect fees for using them, in virtual stores and markets);
d. Enjoying "chillul Shabbat" (in commercial sites);
e. "Mar'it Ayin" and "Chashad" (suspicion);
f. "Ziluta DeShabbat" – disrespect for Shabbat.
We shall discuss each one separately and we'll check in each one if the owners transgress the above prohibitions.
A. "Lifney Iver" ('putting a stumbling block before the blind') and "Mesaye'ah Le'overy Aveira"
The Torah warned, "Before a blind man you shall not put a stumbling block". This prohibition includes causing a Jew to fail by transgressing a prohibition. Since the Internet user who surfs the web is definitely transgressing prohibitions from the Sages (Miderabanan) and maybe even from the Torah (Mide'oraita), one needs to discuss if when the owner of a site leaves it working on Shabbat, he is thereby transgressing the prohibition of "Lifney Iver" or of assisting a transgressor.
The Gemara says that one does not transgress the prohibition of "Lifney Iver" unless the person being caused to fail could not have transgressed the prohibition without the help of the person causing to fail. Therefore, when there are other similar sites, one can say that there is no prohibition from the Torah of "Lifney Iver". However, this does not apply when regarding a unique site, which does not have other similar sites, or regarding the kind of sites, which are operated mainly by Jews. However, there is a disagreement in the Rishonim, regarding a case where the transgressor could have transgressed the prohibition even without the help of the person causing him to fail, whether or not assisting him is prohibited from the Sages – the Rema cites two opinions and concludes that one who cares about his soul should be stringent. However, when regarding the prohibition of assisting a transgressor, which is from the Sages, there are opinions of Achronim that the prohibition does not apply in the following situations: assisting someone who converted from Judaism, assisting someone who transgresses purposely, assistance which isn't close in time to the transgression, and assistance when the transgression isn't done with the item given by the collaborator – the person failing the other – to the transgressor, and these cases are connected to our issue.
Another reason to support the opinion that keeping the site running does not transgress the prohibitions of "Lifney Iver" and assisting a transgressor is that one is given permission to assume that the users of the site are non-Jews or that no one will use the site.
It may also be that there is no prohibition of "Lifney Iver" and assisting if at the time of the transgressions the collaborator is totally passive.
When closing the site on Shabbat involves money loss, such as losing non-Jewish customers or where the technical solution is problematic, one can add to the permit the opinion of those who say that there is no need to spend money in order to refrain from transgressing the prohibition of "Lifney Iver".
B. "Mimtzo Cheftzecha" – the prohibition of sales on Shabbat.
In sites which provide financial and commercial information, etc., it is clear that the consumer entering the site and reading the information is transgressing the prohibition from the Prophets: "Mimtzo Cheftzecha VeDaber Davar", a verse from which the Sages learn that one may not study his assets on Shabbat.
In sites which collect money for information or any service or that a payment is given for ordering a certain item, the buyer is also transgressing a prohibition from the Sages of commerce on Shabbat, and he is certainly transgressing the prohibition of "Mimtzo Cheftzecha".
On the other hand, the provider of the service or the seller, who is totally passive on Shabbat, is apparently not transgressing these prohibitions. However, in order to be in accordance with all opinions, one should make sure that the buyers' credit cards will be charged only after Shabbat, and that this information is publicized in the site in a place where everyone can see.
C. Shabbat Salary
The Sages prohibited accepting the salary of working on Shabbat, even for doing a permitted action, and there are Halachic rulers who wrote that this prohibition applies also to renting out one's belongings on Shabbat, and such was ruled in the Shulchan Aruch.
One needs to discuss if there is a problem of 'Shabbat Salary' ("Sachar Shabbat") when collecting payment for services provided on the Internet, also on Shabbat, or for buying an item, which was ordered on Shabbat from an operating commercial site.
It seems that if the payment for using the site is monthly or yearly, there is certainly no problem, since it is considered a salary, which is covered up or intermingled in the rest of the salary, which is permitted. Also payment for an item ordered on the Internet is certainly not Shabbat Salary.
However, receiving a one-time payment for information, watching a movie, downloading music, etc. is indeed prohibited, since it is similar to receiving payment for renting out one's belongings on Shabbat, etc., and this is the law also in the case of a site which has a virtual market, where the owner of the site receives a percentage of each transaction which takes place there. Therefore, such a site could be operated only in partnership with a non-Jew where each person profits from a certain day. Only in the case of great need and great loss of money may one rely on the lenient opinion that one can receive the percentages without a partnership with a non-Jew.
D. Enjoying "Chillul Shabbat"
The prohibition to receive enjoyment for the desecration of the Shabbat is only regarding enjoying the thing itself through which the Shabbat was desecrated, but not regarding the salary given for the "chillul Shabbat". Therefore, in the cases being discussed there is no problem of enjoying the desecration of Shabbat, especially since other people may receive enjoyment from the desecration of the Shabbat right after Shabbat. All this is under the condition that the owner of the site did not transgress any prohibition by leaving the site open on Shabbat (as elaborated in A), since if the site was operated in a prohibited manner, it appears that the owner may not receive the salary for this work.
E. "Mar'it Ayin" and "Chashad" (suspicion)
The Sages prohibited doing on Shabbat a number of things for fear of "Chashad" (suspicion) of "Marit Ayin" (the appearance of things) – where the observers might suspect that the person doing these things is transgressing a prohibition, even though the actions themselves are not prohibited. For this reason the Sages prohibited renting out a bath-house to a non-Jew for Shabbat even if it is rented out by share of profits – since the bath-house is known under the name of the Jew, and the non-Jew does in it prohibited work on Shabbat. The fear is that people who don't know that the non-Jew has share of profits (and therefore operates the bath-house for his own good) and might think that the non-Jew is the owner's worker, and they will suspect that the owner is transgressing the prohibition of telling the non-Jew to do a prohibited work on Shabbat. Indeed, there are Halachic rulers who wrote that one may not permit placing an automatic vending machine in public, if it is known to be a Jew's, and there are those who wrote the same also about an automatic teller machine.
However, it seems that in this case there is not fear of "chashad" and "marit ayin" since everyone knows that these machines work automatically, without the assistance of man, and if so, what "marit ayin" might there be here? Therefore, it seems that also in leaving a regular or commercial internet site open on Shabbat there is no problem of "chashad" and "marit ayin", even if it is known to be a Jew's (for example, through the ending .il, etc.), since everyone knows that the site works automatically, without human intervention. Additionally, one may say that there is no law of "chashad" and "marit ayin" in a place where there are no observant Jews and cannot be observant Jews, since the whole fear of "chashad" and "marit ayin" is when an observant Jew might suspect another observant Jew that he is transgressing a prohibition. Additionally, we may say that since there is no source for the decree of "marit ayin" in new cases such as these, we may not add such decrees.
Maybe, ideally (lechatchila) one should add a specific note that any order made on Shabbat will not be handled until after Shabbat, and then there is no fear at all.
F. "Ziluta DeShabbat" – disrespect for Shabbat.
In the Responsa Igrot Moshe, he was asked about the possibility of a Shabbos-Clock turning on an oven so that it begins cooking or baking the food about an hour before eating. In his answer he wrote, among other things, that "there is a good reason to prohibit for another reason, which is 'ziluta deShabbat' and even 'ziluta de yom tov' which prohibits a number of things. Since it is clear that there is disrespect for Shabbat in this prohibition, even if it was not specifically prohibited, since the prohibition is itself the idea of disrespect. And it is simple, in my opinion, that a person who does something which is disrespectful to Shabbat is transgressing the obligation to honor Shabbat which is an obligation from the Torah which was explained in the Prophets…"
In the Responsa Chelkat Mechokek, the author was asked about leaving an electronic answering machine open on Shabbat so it could accept business orders, and the orders will be dealt with after Shabbat, and he answered that "…and besides that, this is what the Sages were talking about when they said 'sages be careful with what you say'. When the technique steps a few steps forward, and one day a person might be able to set up a big shop automatically and one can set the store to open at the right hour, and the buyers will come even with no one there, because the merchandise will given out in exchange for the money which they put there, and if we disrespect Shabbat with technical matters, where everything is done on its own, a great desecration of the Shabbat will be born, where a person, while sitting in the Beit Midrash or dining his Shabbat meal and singing songs for Shabbat, and his office or business will be operating normally like on a weekday. I doubt if this isn't like the case the Ramban talks about in Parshat Emor about regularly done commerce, even concerning things which aren't actions prohibited from the Torah… and even if there is a big difference, since the Ramban talks about a case where a person works hard with him on the Shabbat and with effort, and this isn't the same when a person is not doing anything at all, and all is done by the machine before the Shabbat. In any case, the fact that a person's commercial business is operating publicly on Shabbat, means that this is not a day of rest, and in any case it doesn't disclude "uvdin de'chol" (weekday type actions) or "marit ayin" before the public who don't know the laws of the Torah, and of course "zachor et yom hashabbat lekadsho", where one's actions on Shabbat should not be like during the week, is not fulfilled. And this is not like the permit concerning an automatic vending machine, which stands in the public with no name and ownership, where people do not know to whom it belongs. It is different when a person does such a thing in his house and property… and when one allows commerce and acquisitions to take place also on Shabbat, even with the permit of the Torah, this can cause the holiness of the Shabbat to be desecrated and disrespected very much. My son, refrain from such a thing".
Regarding these words of the Chelkat Mechokek, the author of the Responsa Be'er Moshe writes: "I saw in the Responsa of the Chelkat Mechokek that at first he wrote as I did that according to the Halacha there is no reason to prohibit. However, afterwards he made himself the Dayan of decrees, and decreed a new decree, when there is no doubt that no Rabbi, whomever he may be, can decree new decrees. Certainly, if the greatest of the Rabbis of our time will decree a decree, and will agree upon it, we shall accept it upon ourselves, however a single Rabbi may certainly not decree, and we will certainly not accept it upon ourselves".
However, we may note that the Igrot Moshe spoke of a case where a person does an active action on Friday which will cause disrespect of the Shabbat (he sets the timer to turn on on Shabbat), as opposed to the case of the internet, where a person only refrains from shutting down the site. The Chelkat Mechokek wrote about a person who leaves in his house an electronic answering machine, and this is considered in the public, etc. One may doubt, however, if the operation of an Internet site is considered public (it is certainly not in a person's home). Maybe, one should distinguish between a site that specifically belongs to a Jew (or has the .il ending – which is mostly Jewish-owned) and a site, which is not, considered a Jew's.
Also for the definition of public ("farhesia") one may distinguish between sites, which serve the general public, and sites, which serve mainly Jews.