Do believe that not every question here gets answered in 24 hours. There are a few tools you can use in the meantime.
1. The FAQ
2. THe Search Facility
3. The Ask Dr. Bonsai Robot on the
startpage
Please begin by searching on "yellow leaves" or reading the faq on watering. The vast majority of tree problems are caused by improper watering and keeping the wrong plants indoors.
In the event you are watering properly and have the plant outdoors and are still having problems, please answer the following questions:
1. What kind of bonsai do you have and how long have you had it?
2. Where did you get it, and what was its condition at the time you acquired it?
3. When did you notice the problem?
4. How have you been watering it and how frequently?
5. What region are you located geographically and where are you keeping your tree, indoors or out, full sun, part sun, shade?
6. Does the soil have any unpleasant odor?
7. When was the tree last repotted?
8. Is there any discoloration of the foliage? Would you describe it as turgid and green, dry and brown, wilting, mottled or partially eaten? If you brush the foliage with a fingertip, does it fall off?
9. Is there evidence of pests, like ants or aphids?
10. Can you post a picture of your tree to the forum?