Exporting a single state button
To export your web button click on File -> Export to open the "Export" window.
After opening the "Export" window, select the directory-destination you want your button to be exported to, the file type you want it to be exported as (.jpeg, .png, .gif), define its attributes (quality of the end result), and click on the "Export" button. The better the quality, the bigger the file size.
In the .png file format you also have the option of saving your button image along with an Alpha channel in order to add transparency to your button image.
Example:
Free buttons by webbuttonmaker.com
Button maker by Likno Software