Your MacBook is NOT overheating. It is quite normal for Macs to get hot during intensive operations, and it is also normal for the power adapter and the charging port to get very hot while charging. It is not a fire hazard, nor is it dangerous.
Apple Portables: Operating temperature
The bottom of your Apple portable may become warm during normal use. If the computer is on your lap and gets uncomfortably warm, remove it from your lap and place it on a stable surface.
The Intel processors used in Macs are designed to automatically shut down to prevent damage if they truly overheat. CPU Tjmax = 105C (221F), GPU Tjmax = 100C (212F) on i3, i5, i7 processors. (Source:
Intel)
If you're not already using it,
iStat Pro (free) or
iStat Menus ($16) will give you accurate readings of your temps and fan speeds, among other things.
Unless there is a rare defect in a Mac, most temps are well within the normal operating range, considering the workload being put on it. Websites with Flash content, games and other multimedia apps will put higher demand on the CPU/GPU, generating more heat. This is normal. If you're constantly putting high demands on your system, such as gaming or other multimedia tasks, expect temps to rise and fans to spin up accordingly. It's just your Mac doing its job to maintain temps within the normal range.
It is also quite normal for your Mac to become extremely hot to the touch during intensive operations. The aluminum body transfers heat more effectively than other materials used in computer casings, so you will feel the heat more. This doesn't indicate that it's overheating and will not harm the computer to be hot to the touch.
Your fans are always on when your Mac is on, spinning at a minimum of 2000 rpm (for MBPs) or 1800 rpm (for MBAs, MBs and minis). iMacs have 3 fans with minimum speeds in the 800-1200 range. They will spin faster as needed to keep temps at a safe level.
If your fans are spinning up without increased heat, try
resetting the SMC.
(PRAM/NVRAM has nothing to do with these issues, so resetting it will not help.)
The intake and exhaust vents are in the back of the computer near the hinge on all Mac notebooks (except the new MBP with retina display, which has intake vents along the sides at the bottom). The iMac vent is a slot on the back near the top of the computer. Make sure the vents remain unblocked to allow your computer to perform at its best.
Learn about the fans in your Mac
Apple Portables: Operating temperature
For Flash-related issues:
Unless its in °C you don't have anything to worry about 