Automatic transmission I have an honda civic 94 LX, I want to know if THE TRANS FLUID has to be checked on cold or hot engine. AND I am having a problem with the transmission when i am driving fast like 50 mph and stop accelerating it makes a noise like skipping the gears, but when the car slows down it disappears

Fluid can leak out of the driveshaft seals, the input shaft seal, the transmission pan gasket, the torque converter or the ATF cooler and line connections. If the fluid level gets low, the transmission may be slow to engage when it is shifted into drive. Gear shifts may be sloppy or delayed, or the transmission may slip between shifts. If the fluid level is really low, the transmission may cause the vehicle to not go at all.fluid level should be checked when the fluid is hot with the engine idling, the parking brake set and the transmission in Park. If fluid is needed, add only enough ATF to bring the level up to the full mark. Do not overfill because doing so can cause the fluid to become aerated, which may affect transmission operation. If the dipstick reads low, the transmission is probably leaking. So look underneath to see where the fluid is going. If there are no visible leaks, check the radiator for ATF in the coolant. The ATF cooler inside the radiator may be leaking and cross-contaminating the fluids.
You should also check the condition of the fluid. Some discoloration and darkening is normal as the fluid ages, but if the ATF is brown or has a burnt smell, it is badly oxidized and needs to be changed. Varnish on the dipstick is another indication of worn out fluid.
You can also do a "blotter test" to check for worn fluid. Place a few drops of ATF on a paper towel and wait 30 seconds. If the spot is widely dispersed and red or light brown in color, the fluid is in satisfactory condition. But if the spot does not spread out and is dark in color, the ATF is oxidized and should be changed.
Many transmission experts say most transmission problems can be prevented by changing the ATF and filter regularly for preventive maintenance. How often depends on how the vehicle is driven. For some vehicles, this might be every 30,000 miles or two years.
The harder the transmission works, the hotter the fluid runs. The life of the fluid drops quickly once its temperature gets up above about 200 degres F. Installing an aftermarket auxiliary ATF cooler that is parallel to the OEM ATF cooler is recommended to keep fluid temperatures down on vehicles that are used for towing or are driven hard.
ATF also becomes contaminated with normal wear particles from the clutch plates, bushings and gears. The filter will trap most of this debris before it can cause problems. But many older Asian transmissions only have a plastic or metal screen that does little to protect the transmission against internal contaminants and nothing to keep the fluid clean. On these vehicles, changing the fluid is the only way to get rid of these contaminants.
When adding or replacing ATF, use the type specified by the vehicle manufacturer. GM, Ford, Chrysler, Honda, Mercedes and others all have their own specs for ATF. There is no such thing as a "universal" ATF that works in all transmissions. Some fluids meet a variety of specifications, but cannot meet them all because of the different friction additives that are required.
Ford has three automatic transmission fluid specifications: Type F (a non-friction modified formula for most 1964-81 transmissions), Mercon (a friction modified ATF similar to Dexron II for 1988-97 transmissions), and Mercon V (Fords latest friction-modified formula, introduced in 1997).

When will you people learn that on hondas you check ATF level with the engine OFF after few miles drive ;stop the engine wait 1 minute and then check

You always check trans fluid hot, due to the quantity of fluid the level will vary by about 1/2 quart due to heat expansion.