If you seek out the original record, or even the "original" microfilm the record was copied from, you might find additional documentation and records. Or you might simply be able to obtain a copy superior to the one available online. When records are put online they are usually done in very large quantities at a very fast rate, which almost always seems to lead to errors. Who hasn't tried to read a washed out census page and wondered how it got past quality control?
Take for example the Georgia Archive's Virtual Vault. They have a ton of great information online, including land records, death certificates, and marriage records. I've found so many original documents through their site, such as this marriage record for my GGG-Grandfather, Thomas T Albea:
But last time I went down to the archive, I went ahead and pulled up the marriage records on microfilm. Here's the same record:
A huge difference huh? The image online is faded and light, whereas the second is nice and dark. Also, the original image is low resolution that doesn't get much bigger than what you see here, whereas the second image is of much higher resolution and can be viewed at a much larger scale. When I pulled up the record in person, I was able to adjust the brightness and contrast how I wanted and then save a very high resolution copy to my flash drive. I'll be able to do a lot more with the second copy than the original.