Besides the English character, if you want to use other characters in your web application, please try the following:
1. Locate Web.config under C:\Inetpub\wwwroot\appeon\AEM on the machine which has Appeon Server installed.
2. Open Web.config with notepad and modify in the "globalization" line as show below:
<globalization requestEncoding="utf-8" responseEncoding="utf-8" uiCulture="auto" culture="auto" />
3. Save the changes to the file.
4. Restart IIS.