When you have a web site where your visitors can interact with the site and leave things on the site for other visitors to see you need a Terms of Service agreement. This agreement needs to specify precicely what your visitors are and are not allowed to do in interacting with your site and what use you are allowed to make of the material that they add.
Just linking to your Terms of Service from the bottom of the page isn't enough as that just makes it easy for them to claim that they never saw the link and therefore didn't agree to what your Terms of Service specify. The Terms of Service (let's abbreviate that to TOS) need to be agreed to by both parties if they are to have even a slight chance of being able to be enforced.
The only time that you can get away with just linking to your TOS at the bottom of the page is where you are not placing any restrictions on what your visitor can do and are simply clarifying the very strict limits that you are applying to yourself with respect to their material. So if your TOS specify that they can post what they like, they retain full ownership of what they post, that they can remove what they posted at any time, and you will make no use of their posted material anywhere other than where they posted it, then you can just link to the TOS that specifies that at the bottom of the page since the only time that a TOS that specifies that will be of concern to your visitor is when they decide that they want to confirm that they haven't given you any rights over the material that were not implicit in their having posted it.
The least that you need to do if your TOS is less restrictive on you than that or more restrictive on them (and just about all TOS will be) is to at least sumarise those differences o the page where they post their material from and refer them to your TOS for more details. That way they are at least aware of the key points when they make their post in the first place. For example on the page where I allow visitors to enter questions that they can then email to me I have a sentence in bold at the top of the form that clearly states that using the form gives me permission to publish their question anywhere I want to publish it. The form itself allows them to remain anonymous and so any identifying information that they supply with the question is their choice. Since they can easily see from the page that they can limit their identifying information but that if they include it in their post then I may include it with their question when I publish it the situation is clear without needing to ask them to agree to a substantial TOS. Should anyone subsequently complain tha tthey didn't agree to their name appearing with the question I can clearly demonstrate that there is a checkbox on the page where they must have agreed in order for my to have included it in the first place and I'd remove their name straight away if they asked in any case.
Where there are a lot more alternatives relating to someone making multiple posts over a period of time (for example on a forum) then a more substantial TOS is needed and the TOS would then need to be written out in full on a separate page. Just linking to the TOS from your form isn't enough in that situation. You need to have some way of demonstrating that the person saw the link and has actually agreed to what the TOS says. Now you can't force anyone to actually click on te link and even if they do then there is no way to tell if they actually read everything in the TOS. What you can do though is to ask them to take an action that confirms that they agree to abide by what the TOS says. If you have proof that they have agreed to it then whether they actually read it or not is then up to them. They have agreed to it whether they know what they are agreeing to or not.
Now any sensible person will have at least scanned through what your TOS says looking for anything they'd object to prior to stating that they agree to it. The more sensible ones will actually print off a copy so as to be able to clearly show what the TOS said at the time that they agreed to it so that if you subsequently change the TOS and do not ask them to agree to the changes that they will be able to show what they actually agreed to.
The simplest way of obtaining their agreement to the TOS is to have a checkbox o te form that they must check to say that they agree to the TOS and where if they don't check it then you don't allow them to interact with your site. If you are worried that they might be able to claim that they didn't realise what the checkbox was for and just went down a column of checkboxes on your form checking them all then substitute a text field for the checkbox and get them to enter their name to indicate that they agree to the TOS. If you want to make it absolutely clear then get them to copy the TOS and paste it into a textarea in the form and then validate that they haven't hanged anyything in it.
Whatever you do there will still be the possibility that one of your visitors will claim that they were totally unaware of your TOS. The more explicit you make the option in your page where they indicate that they agree to it the more likely that you will be able to prove that they have said that they agree to it. Just how explicit you need to make it depends on how likely it is that someone is going to challenge you over it in the future and that depends a lot on what your TOS says. If your TOS doesn't try to claim any more rights over their material than are reasonably implied by their posting it in the first place then there are unlikely to be any challenges to it and so you will not need to make it awkward for your visitors by making them do more than is really needed to indicate their agreement.
A lot also depends on what you would be prepared to do if someone does decide to object. If you are happy to remove all reference to something if the person who priginally posted it asks you to then they are going to be less likely to be able to pursue a claim that they never agreed to your publishing it in the first place than they will be if you are going to insist on keeping it. So if you want to be able to keep their material published on your site regardless of if they change their mind and ask you to remove it then you will need to have a far stricter method of capturing their agreement allowing you to do that.
If you are having any trouble deciding to what extent you need to go to record your visitors' agreement to your TOS then perhaps the safest option is to err slightly toward obtaining a more definite response from them that they agree. If you are trying to decide whether to get a confirmation of their agreement at all then provide a checkbox. If you are trying to decide whether providing a checkbox is enough then get them to type their name. It is far easier if you later decide that you are asking for too great a response to simplify it down since there you don't need to go back and ask everyone all over again as you would if you are going to increase what you require them to do.
This article written by Stephen Chapman, Felgall Pty Ltd.