Is there a funny odor coming from your dishwasher?
If so, this problem should be addressed quickly, by yourself or a dishwasher repair professional, because it could correlate with bacteria and other grossness on your dishes. The machine itself might have a gross smell or it could just not be running through its cycles effectively. If the odor only happens sometimes, that's an even bigger cause for concern.
You can sometimes diagnose this issue based on the kind of smell. Is it like a chemical odor or burning plastic? A container might have fallen down onto the element and melted. The material will completely evaporator as the element gets very hot. Likely, the container will be melted over the element and stuck there so this issue is easy to notice.
What if it's just a gross, bad food smell? Try running an empty load with a little distilled white vinegar. Also, take out the screen at the bottom of the dishwasher tub where everything drains out and clean it off. You can use a toothbrush and a little soap to get all the dirt and grime out. You should also check to make sure nothing is stuck in the drain as this could cause a bad odor to stick around for quite a while.
Additionally, get into the habit of pre-rinsing your dishes. Don't put them into the dishwasher with a bunch of sauce - especially if you don't plan to run your machine right away. While the dishes will likely get clean, chances are some of the contents will get stuck in the machine, the spray arms, chopper blades, screens, filters, etc. The result is a stinky, foul odor that is not always easy to get rid of.
Always make sure to keep your dishwasher clean. The most obvious place to look for dirt, debris and leftover food is the drain. Take it off and clean it out, check around in the opening to see if anything got through too. Clean the drain pump and hose out completely. Also, clean the spinning arms, dishwasher detergent dispenser and door seal. When cleaning out the drain of your dishwasher - you can remove the big objects with your hands but a soft-bristled toothbrush will work better for cleaning out smaller objects.