I gather that one can size things on photobucket now, but many of the photos I show are from google images and they can wildly vary in size. Sort of like elephants can.
If you need to see how to show the google photos, go look at the Blog at the bottom of the page, on the far right of the dark blue strip - it shows you how to place pixel information - if you look at September 2008.
I've found that the highest pixels for width without overflowing the page are 900 or maybe slightly above. You see the pixels either on google image, which gives them, or on your image, if you click "see image on other page". They'll be on top, or at least are on my computer. (I use an old mac, so how to see image on another page does vary but should be fairly easy).