I have two adsl as Wan,but everytime after I re-dial pppoe-out* again,the four dynamic "change MSS" which originally are placed in first four position would down to the bottom like what shown in the following picture, I found that would causes many pictures in web page can't open.
Is there a command that can reorder the sequence in mangle by scripting?

In your case dynamic rules and static rules are in different chains, and it won't make any difference if you move dynamic rules up.

In your case dynamic rules and static rules are in different chains, and it won't make any difference if you move dynamic rules up.

Do you mean that dynamic rules of "change MSS" is redundant ,and useless? because I have set "passthrough" is "no" in the frontal rules, so that means if "change MSS" down to the bottom,it can't change mss of any packets which be intercepted by the frontal rules.

No, I mean that change-mss rules are in "forward" chain but other rules are in "prerouting" chain. Those two chains are independent.
Here you can read more about chains:
http://wiki.mikrotik.com/wiki/Firewall_filter#Chains

And here you can see packet flow diagram
http://wiki.mikrotik.com/wiki/Packet_Flow

No, I mean that change-mss rules are in "forward" chain but other rules are in "prerouting" chain. Those two chains are independent.
Here you can read more about chains:
http://wiki.mikrotik.com/wiki/Firewall_filter#Chains

And here you can see packet flow diagram
http://wiki.mikrotik.com/wiki/Packet_Flow

Do you mean that whether the position of "change MSS" is in the first four or last four that makes no difference?

It would make a difference if you had any other mangle rules in the 'forward' chain. But you don't. Rule order is only important within the same chain.

It would make a difference if you had any other mangle rules in the 'forward' chain. But you don't. Rule order is only important within the same chain.

oh,I see, thank you very much.