sig is correct. Anything you can set up you'll be able to disable.
If you still want to give it a try I think you'll need to create a new account and in System Preferences : Accounts you can enable Parental Controls on an account. From there you should be able to limit internet usage.
PC limits web content, & access to the computer/certain apps, but doesn't allow time limits for internet access.
There is/was a small paid-for app that prevented web-access for a period of time after clicking a button ( and was presumably more than a click to disable ). I forget the name, and looked for it recently w/o success. Intego & others sell more expensive solutions.
Parental Control wrecks Hotmail. Does this matter to you?
See below:
Apple Parental Control:
Content has only three choices:
1) Unrestricted access;
2) Limit access to adult websites automatically;
3) Allow access to only these websites.
Only the second choice allows “customize”.
In other words, you have to turn the filter on, then try to bypass it.
But the filter shuts off Hotmail, and I can’t find a way to bypass it for this site. The Apple tech guy said to look at the blocked log and allow what had gotten blocked, because Hotmail won’t be blocked as www.hotmail.com, but as one of the many addresses it uses to connect. Nothing shows a blocked. I can’t accomplish unblocking Hotmail.
In fact, even when “unrestricted access” is selected, Hotmail remains blocked on Firefox. The only way to get it back is to go to Accounts (under System Preferences) and make the accounted “Unmanaged”. There is nothing in Logs under Parental Controls showing anything has been blocked. Hotmail opens in Firefox but at the top it says, We can't connect to Windows Live Hotmail right now. Please try again later. And email, though it shows, doesn’t function.
So first, there’s a software glitch. Then you somehow have to know (or find out) that Parental Control on an account isn’t removable under Parental Control—but requires going to Accounts.
There is no option to simply block certain sites. Only after turning on the filter can you do this.
Bottom line: Useless.
Safari with filter on denies access to Hotmail, but leaves no blocked site log. Turn the filter on, and all is okay.
For Firefox, however, Hotmail is blocked until the whole Parental Control is turned off. Or even after, until the computer is turned off and then on—which finally clears it.
