One website is blocked by fortigate. No web filter is on.

Out of curiosity I tried looking into this for you.  I can replicate your issue with not being able to access this website, but I can do it from any network whether behind a FortiGate or not.  NMAP seems to think that the website is listening on 80 and 443 though so I was somewhat confused. 

So I ran Wireshark packet capture and apparently the website is providing the TCP 3-way handshake but nothing further.  When my browser does a GET, it responds with a mere acknowledgement and then closes the connection (RST,ACK).

I used a web-based service to check the site's availability and the only server that seemed to think it was actually up was based in Israel, so maybe they have some special web filtering in place.  Either way the issue is definitely on their end, so no worries with your config or FortiGate device.

The fortigate is NOT blocking you.  That site is not reachable.

When in doubt use "diag debug flow"  and inspect the output.

oh forgot to add, it's expired due to a routing loop at 

16 180 ms 184 ms 179 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 17 * * * Request timed out. 18 182 ms 186 ms 181 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 19 * * * Request timed out. 20 186 ms 185 ms 185 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 21 * * * Request timed out. 22 214 ms 188 ms 191 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 23 * * * Request timed out. 24 189 ms 198 ms 186 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 25 * * * Request timed out. 26 188 ms 192 ms 200 ms bzq-166-168-31-133.red.bezeqint.net [31.168.166.133] 27

Ken Felix