Bad image Hello to you all... My S1 IS from one moment to another has shown a problem... I can point e focus normally but after de shoot the preview is very BAD and the image saved is the same of the previewd one... The pictures have real bad resolution and light and many strips with rainbow colored edges... Some people told me something about the shutter curtain or something like that... It makes any sense?

Something must be wrong on the camera. Did you try to press the display button several times?
Dis you remove the battery for a few moments and replaced it?
Just a few things you could try before you think it is really defect.

I presume you're asking about a Digital Rebel and not a 35mm film Rebel (as per the question heading).

If so, that's probably normal. It's only relatively recent dSLR models which have a "live preview" facility (often wrongly called "live view"). The whole point of an SLR is that the viewfinder is the main compositional viewing tool; the LCD is there solely to display and adjust camera functions and to review images already captured.

Most current and recent SLR's now have live preview, and all true SLR's are incapable of viewing the image at the actual moment of image capture as the viewfinder mirror must flip up out of the way of the image sensor.

If you want live preview then you must change your camera. if you tend not to use the viewfinder anyway then consider mirrorless Compact System Cameras such as the Olympus and Panasonic Micro Four Thirds models as they do have a true live view capability and the LCD is the main (or only) tool for composing images. Panasonic also have their regular Four Thirds G range, which look like an SLR but have an electronic viewfinder and they are also capable of true live view.

Which camera body do you own? It is the camera that determines where to focus and when you are in focus or not. I have 3 Canon film bodies and two digital. On all, the camera can be set to detect focus using all or a specific focus point visible in your viewfinder. Check how you have the camera set and choose ONE focus point. place this focus point on your most critical item in the image, in the case of your birds, the HEAD of the bird, press your shutter button half way to lock exposure and focus, then shift the aim to compose your image before pressing the rest of the way to make the exposure.

For birds, on my digital cameras, I choose to go into live preview mode, zoom in to 10x magnification and manually focus. This eliminates the camera not knowing what I want in focus.

try using a tripod to steady the shot, and do not forget that Canon states you should turn off the IS when the lens is used in conjunction with a tripod. From firsthand experience, I agree with this instruction, often when stable on a tripod, the IS can actually be trying to correct for its own movement and cause a degradation in image focus.

Good luck

Page 140 of your manual "Bracketing Programs" . This camera seems only to be able to do a 3 frame bracket. Normal , Over , and Under exposure. Set the auto bracket to (3) frames, set a 2.0 bracketing increment the order is not really that important. Normal however should be your first frame shot. Make sure that only the speed changes in the different exposures not the aperture this would lead to de-focused images. One you have the three images you will have to bring them into ©Photoshop or ©Photomatrix Pro to create your HDR file. The camera will not create this HDR on its own. there are plenty of HDR tutorials on YouTube. Use a tripod ond a cable relaes when you are shooting in order to reduce movement in you images.

Well, stupid me, I didn't realize there is a diopter adjustment button directly to the right of the viewfinder. I would NEVER have known it was there, but after asking my photo-nerd friends all of a sudden the solution was apparent. Still a wasted day of shooting, but hey now I don't have to look like an idiot taking my camera somewhere to be serviced!

There are two modes to the XS's Live View system, selectable via Custom Function 7. Live View is disabled by default, by the way, so you'll need to find this menu item in Settings Menu 2 to turn it on. The two options are called Quick and Live modes. Quick mode works as most Live View modes do, dropping the mirror when you press the AE-Lock button (marked with an asterisk) to use the conventional phase-detect autofocus system. This temporarily blacks out the Live View image, which makes it impossible to know that you're still framing the subject and holding your AF point in the proper place.
That's why they added the second mode, which they call Live, but is better described as contrast-detect autofocus. This works just like a digicam, reading the image from the imaging sensor while adjusting the lens for the setting that produces the most contrast in the image. A small square appears in the center of the image area, and you can move it around with the cross keys. Just like Quick mode, unfortunately, you have to press the AE-Lock button first until you hear the focus confirmation beep, then press the shutter button to fire. It's a little slower at times than phase-detect mode, but it gets the job done. Live mode is really better for tripod work, where you can place the AF area right where you want it and confirm focus onscreen.
Both modes offer the ability to zoom in on your live view, excellent for confirming focus before capture. Using the Magnify button just right of the AE-Lock button, you can zoom in 5x or 10x, then press the AE-Lock button to focus if you like; but of course you can't confirm framing in that mode.

Try cleaning your sensor manualy.

DSLR camera was not made to be used as a point and shoot camera and you cant preview the shot before taking a picture. You are to use the eye piece to focus right. Also before taking a picture, push the exposure button just a little to let the camera focus right.

I wouldn't blame your wife's grandfather. This might be a defective CCD imager. If so, Canon should fix this for you for free, including free shipping both ways. This is regardless of your camera's warranty status. Please check the following two links for more info:
http://camerarepair.blogspot.com/2007/11/canon-digital-cameras-showing-black.html

http://www.usa.canon.com/consumer/controller?act=PgComSmModDisplayAct&fcategoryid=225&modelid=13390&keycode=2112&id=29819

Applicable cameras include:
A40, A60, A70, A75, A80, A85, A95, A300, A310, S1 IS, S60, S200, S230, S330, S400, S410, S500, SD100, SD110, IXUS V2/300/400/430/500, IXY Digital 200a/300a/400/450/500

Its possible that there is a CCD issue with your camera. I've been reading more and more people are having CCD issues with the S1-IS. The CCD is the part of the camera that captures the image, and usually they distort or do some funky things with the pictures. Its entirely possible they would knock something out of focus.