Edit->prefs->configs->accelerators
At the top of the file you will see options for middle-clicking links to open them in background layers.
Lower down you will see options for CTRL+right or left clicking to open in new layers or open in new background layers.
Also, if you type about:config in the address bar, then search for tab, you should see this:
browser.tabs.loadInBackground
Set that to true, that will force ALL new tabs to load in the background. (The previous 2 methods only load tabs in the background when you tell it to.)
(If you don't see it, you can add it. Simply right click any other entry and choose new->boolean. Set the name as browser.tabs.loadInBackground and the value as true.)
Also, if you type about:config in the address bar, then search for tab, you should see this:
browser.tabs.loadInBackground
Set that to true, that will force ALL new tabs to load in the background.
Really? Layers are completely different than tabs and KM doesn't have tabs. Can you give me an example site where that pref makes a difference so I can test it?
Not sure. I always either middle click links to open them in the background, or force them to open in the current layer/tab. I honestly don't know for sure whether or not that pref works in k-meleon.