The main reason for this is to help people resize their photo to 90x90 pixels for their avatar, however it will work for any image in a variety of sizes
(helpful for resizing those big digital camera images before uploading to the gallery or forum)
first step open your web browser and go to http://www.picresize.com/
Click Browse
Find the file you wish to resize and click Open
Click on Continue
In the resize your picture section, change the Make My Picture Drop down to Custom Size
Now set the width and height to 90 Pixels
in the Save as section, set the drop down to Gif
Click Im Done, Resize my picture
Now click save to disk to save it to your computer
There are also several free software solutions to do this process, but for one off resizes i find this the easiest