Check your .htaccess file. There's probably something in there blocking the user agent.

It's actually good practice. If we blocked IE users from the internet completely, the world would be a safer, happier place. Good on you for starting the revolution :).

Thank you wheel for your answer.
My .htacces is very simple, i've used the same rules on several sites and it always worked well.
Anyway I deleted it, with non result. Site is still forbidden to IE.

You'll need to restore the .htaccess file.

It likely contains important configuration data for your site.

Yeah, I Know, but i deleted it to try IE.
And even withouth the.hataccess file IE won't show the site!

Something, somewhere is checking for the user agent. .htaccess is one place.

The next two places that I can think of are the apache config file and your script (i.e. check the php code that generates the page).

If that doesn't do it, I would also try IE on a difference computer just to make sure there's not something else in the mix.

Oh, and watch your log files. If you're on linux you can do this:
cat -f /path/to/logfile
which will output the logfile in realtime. Then hit the site in IE and see what the logfile outputs. There may be some clues there.

Thanks wheel for the logifile suggestion.
Meanwhile I tested it on 4 PCs and on two of them (in IE) the site gave the error. On the other two it worked...
:(

are you testing the exact same url string and if so is it a [http://www.example.com/] fully qualified url or just the [example.com] domain name or ...?

yeah, no problem about that,
moreover my .htaccess file reads:

RewriteEngine on
RewriteCond %{HTTP_HOST} .
RewriteCond %{HTTP_HOST} !^www\.domain\.it
RewriteRule (.*) http://www.domain.it/$1 [R=301,L]

tu unify the urls

have you analyzed your server access log to determine how the requests/responses differ for the various user agents?

No, i must download the logs from teh shared hosting, and they seem not to be in real time...