How to load one web page every 12 minutes ?

How about a script that invokes curl to access the web page using any saved cookies that represent your logged in session.

while sleep 720
do
 curl http://the.web.page.com/rest/of/url.html
done

See "man curl"

Or by crontab: Lets see if I can lay this out if you have never done a crontab, but Bob's answer is faster and simpler. Which will be quite obvious very quickly.
sudo pico .crontab gets
# minute hour mday month wday command
*/2 * * * * open http://www.manpagez.com/man/
# */3 * * * * open /Users/dougp/Desktop/Untitled.app
*/3 * * * * sudo /sbin/shutdown -h now
The only active command is the top one and change the 2 to 12 or experiment with 2 and see results. Safari doesn't have to be open and any open page, if it is open, will go to background when crontab loads your called page and reloads at 12 minutes. You'll see. That's why I say use 2 to get the idea. So. copy this: # minute hour mday month wday command
*/2 * * * * open http://www.manpagez.com/man/
in your home directory and save as .crontab then type: crontab /Users/yournamehere/.crontab which sources the file(basically knows it exists now). Then run crontab -l to see if all is listed and crontab -r stops the crontab. If you stop it resource it . Now if you did all this bs, then in either 2 or 12 minutes you should see the man page load. I know there has to be an easier way to explain this. sorry for the verbosity.

doug-penningtons-power-mac-g4:~ dougp$ crontab -l
# minute hour mday month wday command
 */2 * * * * open http://www.manpagez.com/man/
# */3 * * * * open /Users/dougp/Desktop/Untitled.app 
 */3 * * * * sudo /sbin/shutdown -h now

Hopefully this is better

You could look at Platypus
<http://www.versiontracker.com/dyn/moreinfo/macosx/19870>

Platypus will allow you to turn a shell script into a double-clickable application. It has a lot of options, and it might have the kind of kill option you want. It is worth a look anyway.

There is also creating an Applications -> Automator -> Run Shell Script - Workflow.

And finally an AppleScript using "do shell". Some google searches will turn up examples that you can then adapt to your needs (maybe).

In all of these, it is the infinite loop that you want a way to terminate. You may need to experiment with that.

OK, I just created a stupid infinite loop shell script, and wrapped it via Platypus.

I specified a "Output" was a "Text Window".

When I double-clicked on the applications created by Platypus, it displayed a window, with a "Cancel" button.

The infinite loop ran until I clicked on the Cancel button.

So I think you could use Platypus to do what you want without needing to open Terminal.