When a user uploads a photo on Flickr, it resizes it to various sizes and gives viewer the choice to view in whatever resolution (size) he wants.
Similarly, if you want to view or save the original Flickr image, you have to go all the way through the photo page and select Original from the sizes available.
Previously, I have covered a method to watermark your images but in that you needed an app. Here’s a new service that lets you watermark images online without the need of any desktop app.
PicMarkr lets you to add a custom digital watermark to your images online and free. It is useful when you need to protect your copyrights or if you want to add comments to your photos.