Open the image editing program on your computer. Select the "File" drop-down menu and select "New." In the "Width" box, choose "pixels" as the unit of measurement and type in "125" for the value. Do the same for the "Height" box. Select "OK."
Choose a color by clicking on the "Foreground Color" square and use the "Paint Bucket" tool the fill in the blank background with color. Use the "Type" tool to select and apply type to the banner. The resulting button design depends on your skill and creativity.
Save the design by clicking the "File" drop-down menu and selecting "Save As." Type the desired name of your file in the "File Name" box and choose the desired format in the "Format" box. Choose the PSD format first and click "Save." Save the file again, but this time choose the JPEG format. This will put the file in the proper format to be displayed on the Internet.