Hi guys,just wanting some help with this brilliant and terrible game.

As the topic says, I keep having my little summon marks disappear whenever I put them down, even when I plonk them next to a bonfire like everyone else.

Am I missing something? Could someone help as I really would like to take part in some jolly cooperation.

There are certain multiplayer areas of the game, if you leave the area you put your mark it will disappear. Generally any area between a bonfire and the "next" boss is safe, but certain places (like the bonfire by the blacksmith) can be a bit fidgety. If you wanna do coop your best bet is usually to put it either by a bonfire or a boss-door and just stay in the nearby vicinity.

Mine only went missing when someone invaded me.

You can't leave the area or it will disappear. You'll be able to figure out the boundaries based on where fog gates appear during invations or by having your sign disappear as you go through a door. I found it to be a bit of a hassle waiting to be summoned so I used a covenant ring to get summoned as well.

If you literally see your summon sign vanish and you didn't move somewhere and get a message saying your summon sign vanished then you are being invaded. Whenever the fog gates come up and nearby bonfires get extinguished it's a sign that someone is attempting to invade you.

@golguin: keep your banish stone in a slot and when it flickers you know your being invaded.

If they're appearing on the ground then fading away it can often mean your summon sign has effectively been cancelled because someone is attempting to invade you, but failing. Are you human or hollow when you put down the signs? Also, like @ares42 said, some areas are off-limits for placing a sign. An easy way to check for either of these is to have the summon item in your hot-bar and look to see if it greys out a bit to indicate it cannot be used.

it also happens that sometimes someone summons you but fails to do so for any reason....you would have the message "being summoned to another world..." and then nothing sometimes...and may take some time to tell you "failed to invade" later only...

but the reasons evocated before are the most likely