if i have "Lord of D." and a dragon type monster on the field and my opponent uses mirror force,are both of my monsters destroyed or just "Lord of D."? :cool:

Both are destroyed. lord of D. only stops a card from targeting a dragon and Morror Force doesn't target.

but lord of d protects my dragons so i think it should protect the dragon so only it dies

Lord of D. protects dragons from cards that Target dragon type monsters. Mirror force does not target 1 single monster, but all attack position monsters on the opponent's side of the field. A trap that targets 1 monster is something like Magical Cylinder or Nightmare Wheel/Spellbinding Circle.

NO, Lord Of D. only stops effects that TARGET Dragon-Type Monsters, Mirror Force DOES NOT Target.
I've already explained all this hundreds of times, so I'm just going to repeat myself:

Here are 2 easy steps to determine if a card targets or not:

1) Does the card affect 1, and only 1 monster?

2) If so, does the card allow the player to select which monster the effect is used on?

Let's look at some cards:

Change of Heart
Group: Spell Card
Type: Spell
Select and control 1 opposing monster (regardless of position) on the field until the end of your turn.

Does it only affect 1 monster? Yes. Can we select that monster ourselves? Yes. Therefore, Change Of Heart Targets that monster.

Torrential Tribute
Group: Trap Card
Type: Trap
You can activate this card when a monster is Summoned (including Flip Summon and Special Summon). Destroy all monsters on the field.

Does it only affect 1 monster? No, it affects all monsters. Therefore, Torrential Tribute does not Target.

Smashing Ground
Group: Spell Card
Type: Spell
Destroy 1 Monster with the highest DEF on your opponent's side of the field.

Does it only affect 1 monster? Yes. Can we select that monster ourselves? No, the card automatically selects the monster with highest DEF. If that monster were removed or flipped face-down, Smashing Ground would simply go for the monster with the next highest DEF. Therefore, Smashing Ground does not Target

Bottomless Trap Hole
Group: Trap Card
Type: Trap
When your opponent Normal Summons, Flip Summons, or Special Summons a monster with an ATK of 1500 or more, the monster is destroyed and removed from play.

Does the card affect 1, and only 1 monster? This is more complicated and requires you to actually know how the card works. Here's the ruling from Netrep:

Get it?

Creature Swap
Group: Spell Card
Type: Spell
Both players select 1 monster on their respective fields and switch control of them to each other. The battle positions of these cards cannot change during the turn this card is activated.

Again, more complicated (at least, it is for those unfamiliar with the concept) Although Ceature Swap only affects one monster, the monster isn't chosen by us, when we play the card, but rather by the opponent. This allows them to, for example, chain Scapegoat and give us a Goat Token. Therefore, Creature Swap does not Target.
Again, the more official version:

but what if lord of d is in defence?then would my dragon be protected?tell me that.

It doesnt matter if LOD is in defense or attack. Mirror Force still does not target. I believe Dragon-Reborn provided a very good explaination

but what if the lord of d is in defence mode and the dragon is the only attack mode monster on the field,then would it be protected?

No...get this straight...it DOES NOT X100000000000000 MATTER what position Lord of D. is in.

Mirror Force DOES NOT target, even if the only monster's to be destroyed would be your Dragon types, so your Dragon will STILL be destroyed.

The same is with Tribe-Infecting Virus. Even if Dragon's are your only subtype on the field, even if you have Lord of D. or King Dragun on the field, Dragons will STILL be destroyed by its effecr.

Already answred, your dragon would still be destroyed, since Mirror Force never targets, whether it kills 1 or 5 monsters. Your Dragon will always die to Mirror Force.

Actually Dragon reborn from the rulings i have seen smashing ground and hammer shot do target and if something stops their effect say a horus lv6 the effect disappers

You will not find those 'rulings' on the official faq as they do not exist.

Smashing Ground, or Hammer Shot, do not target. They do not allow the player to choose which monster will receive the effect, therefore they are not targetting.

If Horus 6 was the monster that Hammer Shot/Smashing Ground was supposed to destroy, Horus will not be destroyed and the spell card will resolve without effect.

Horus LV. 6 is protected from these cards because of his effect, which protects him from ALL Spells, not just ones that Target. That includes your own Spells, too.