Browsing the web I found 2 solutions when it comes to connecting MOSFET with arduino
Why people sometimes put there this series resistor - it's not on some profesional shields, so why?
What is the reason for that?
Is it wrong to connect Arduino directly to Mosfet without neither series resistor nor pull-up/down res?
Disclaimer: I'm not asking about pull-up/down resistors, I know why they are there:)
You're right. Someone tend to believe that charge on gate may kill an i/o-port. It does'nt.
You can control a MOSFET safely - directly from an arduino ouput.
The capacitance is what worries people, for brief moment in time the io pin has to supply the current, a resistor just ensures the pin does not supply > 40ma
Not really true, big MOSFETs are large capacitances (30nF even) and if you pump out high
frequency PWM to them you'll exceed the pin current spec quite a lot. Also the kick-back
from the drain-gate capacitance has to be considered - that can take the Arduino pin over-
or under-voltage risking latch-up.
Add a 150 ohm resistor (for ATmega based Arduinos) and you don't have to worry.
For fast operation use a MOSFET driver chip anyway.
For the Due you absolutely cannot get away with this, some pins have abs-max of 3mA
and the chip is very easy to fry if you abuse it.
Hi, please use gate resistors.
I have come across failed MOSFETS and they have failed gate to source with no gate resistor, this means you are shorting arduino output to gnd, kills gate drive circuit, kills arduino I/O, NOT HAPPY Arduino.
If gate resistor fitted, most of time output current limited on short, stuffed MOSFET, HAPPY Arduino.
Also gate resistor leads make great and easy access with DMM probes to I/O trouble shoot.
Tom........ 
Thanks guys, clearly it's better to add them.
TG - love you happy arduino comparision.
This may solve the problem of my arduino overheating after I connected it's PWM to l3705n without series resistor.
Since then - even running bare empty it gets warm on usb. On 12V it gets hot.