Right click on an image in your signature, and click Properties. There should be a bit saying Size of File, or something similar. For example, here are the sizes of my signature images: Main Image: 60.06 KB (61503 bytes) Userbar: 6.4 KB (6551 bytes) 60.06 + 6.4 = 66.46KB As this is less than the 100KB limit, it is allowed. To find out the dimensions of your signature, the easiest way is to take a screenshot of your image using the Print Screen function, and paste it into a graphics program such as Photoshop or GIMP. Crop around your signature area, and then look at the dimensions, this is usually displayed in a separate menu, or at the bottom of the screen. If it is under 400px in width, and 200px in height, it is allowed.