Autocomplete feature available in development environments,web browsers and search engines predicts the word or phrase based on the earlier typed words or phrases or commonly used words or phrases(in search engines).It speeds up the process of filling web forms and in logging-in to sites.As all this information gets stored somewhere.So it is possible for trojans to use this feature to gain access to your sensitive data.This feature is enabled by default in most browsers, but can be disabled.

Here are steps to disable autocomplete feature in internet explorer

Open IE.
GO to Tools menu.
Select Internet Options .
Go to Content Tab.
Go to AutoComplete section and click on Settings Button.
Click Delete Autocomplete History button to delete History.
Check the checkboxes for entries you want to use autocomplete for like forms,Address bar and Usernames and password on forms
if you want to be prompted before saving password Check ask me before saving Passwords.