k may be this has been talked about b4 but plz help me out here....i think i don't have any leakage on my map but just wanna be sure. how can i test for leakage? I've tried "Next leak..." from misc menu but nothing happened....so plz some suggestion would be highly appreciated.

compile your map
Open your map in Radiant and go to File->Pointfile
This will display red line through your leaks (if you have any).

The_Caretaker writes...
Yes I did that and did get a huge red line. Plz take a look at this:
http://img152.imageshack.us/my.php?image=leaksh5.jpg
But as far as i know, I don't have any leakage. Incase I do how can i fix it? The line is so random floating in mid air. plz advise me what to do.

Follow the red line from one point to the next, there should be a leak somewhere along it.

Is your skybox a structural brush?

The_Caretaker writes...
I dunno what a structural brush is...if possible plz explain. In case u r wondering how i created by skybox, I made a caulk 1st then gave it a height and appplied hollow. Then i did the corner tweaking. Then i just applied sky on the side and top caulk. by the way i used ctrl+shipt to select the sky surface. I kept a little gap between the the caulk (sky base but no sky applied) and the floor.

Thats the problem then ;)

A 'leak' means that there is a way that light can get out of your map, which must be a fully enclosed space - i.e. no gaps. I recommend you put sky on all 6 inside faces of your skybox, as this allows the texture to work properly (and not look like you're in a box)

how are there 6 sides to the sky box? I thought the bottom of the skybox could be your terrain. Wouldn't that leave just 4 sides plus a ceiling for the sky box?

Everything you make, build or sculpt goes INSIDE the skybox. The skybox is a box (6 faces - 4 sides and a top and bottom) that holds your map. If there is a way for anything to get from your map to outside the box, thats a leak.