Hi Rachel / John - Unfortunately, the screen shot you just posted does not tell me enough to help you. I need details (in written form) that exactly describe your problem, and tell me exactly what you are doing, or trying to do to the image when the problem arises.
For example, are you trying to change the aspect ratio of the image? Are you trying to change the number of pixels in each direction but keeping the ratio constant? What size image are you starting with? What size image are you trying to achieve? Are you first compositing several images, and then need to modify the result of that work? What tool(s) have you been trying to use when the problem occurs, e.g., "image size", "canvas size", crop tool, something else? As you can see, to diagnose a problem remotely, I need much more information than you have provided.
For example,the screen shot that you posted only tells me that on one specific system, at an unknown degree of magnification, one of your images seems to be larger than that particular screen. However, when I look the opening page of your website, I see no such problem on my computer - your images look very appropriate in size with no heads cut off or any other such problem. Because of this, I can't even tell if the problem you are having is a problem with the image itself, or a problem with the programming of your web page (eg, in automatically re-sizing images to fit the windows of different viewers).
Unfortunately, I apologize because I only speak English, so I have to ask you to have someone help you with your written English. It's difficult enough to try to diagnose a Photoshop or web problem remotely, even if the person does speak and write perfect English. However, when there are serious problems in basic communication, it becomes virtually impossible to give help. I have to guess at the true meaning of every word and statement, even more so when the person replies only in short phrases. It becomes a guessing game, and it just doesn't work.
If you can't find someone to help you compose your messages in English, perhaps someone else on this forum will see this thread and help out by translating - just ask.
Sincerely,
Tom M