Putting images online is a bit of a double edged sword, on the one hand you can show your work to many people, many more than was possible in the years before things like Facebook, Twitter, etc., on the other hand, re-sharing may make it harder for people to know a photo is yours, and unscrupulous people/companies may even use your photo without compensation or acknowledgment. Watermarking your images is one way to address the downfalls of publishing your images online.

Like everything in Photography, there are a number of opinions on watermarking images. On one hand, watermarking provides some{{1}} protection to your images, on the other hand, watermarks, especially large marks across the main part of the image, can look bad and reduce the appeal of your images. 

I do put watermarks on my online images, but I try to keep them small, relatively discrete, and aesthetically pleasing. Currently I am using a stylized version of my signature with my website listed. Realistically this does not provide much protection, but it will let honest people find me.

So now do you add a watermark to your images? Many programs, such as Lightroom, have a built in watermarking function. You set up a watermark, either text or a small graphic, and when you save the image, you can automatically add the watermark. For other programs, such as Photoshop, Elements, or even GIMP you can manually add a watermark by creating a new layer and importing the graphic, or typing text.

Again, a watermark is no guarantee of protection, and an unscrupulous thief can retouch your photo to eliminate the watermark, but, in my opinion, a watermark can help honest people find you, and, if done with taste, does not hinder the look of your image too much.

[[1]]although with image manipulation programs such as Photoshop, it is not too hard to remove a watermark if you are determined[[1]]