If you've got a pile of images on your hard drive that need rotating or resizing and you don't have access to desktop image-editing software like Adobe Photoshop (or its free equivalents like Gimp), then an online editor is a good alternative.
Here's a quick tutorial showing how to rotate images easily with Pixlr Express.
Open Pixlr Express
Click here to open Pixlr Express.
When the site opens, you'll see that you have the choice of three buttons - Browse, Open URL or Webcam. The Webcam option is to import an image from your webcam (obviously) - the Open URL button is to find an image on the web that you want to edit, and the Browse button is for uploading images from your desktop. This is the one you will use most.
Upload your image
Click the Browse button to get started. Select an image from your computer and click "Open".
Edit your image
Click the adjustment tool.
Choose from the editing tools
When your image has opened, you can make several adjustments to it. Choose from the available tools. In this case we will select "Rotate".
Click the arrow buttons to rotate the image.
Apply and Save
Click apply and click Save if you have finished editing.
Save the amended image
Rename the image if necessary and click save to save the image back to your desktop.