Not sure on the exact make of your camera but auto-focus cameras have a
number of settings that determine how they focus. I can set my Canon
Digital Rebel to take a focus reading on just one spot, or on 7 or 8 all
at once. You may need to read your manual to figure out how to switch
these settings.

Shooting a subject through foliage would be a classic case where
auto-focus gets into trouble. The camera can't tell what YOU want to see
in focus so it takes its reading from the picture as a whole -- the
foliage probably takes up most of the image area so that's what the
camera focuses on, no pun intended. In cases like this, it's probably
just better to switch auto-focussing off and do it by eye.

Sean

Hi Chris...

Don't know your camera, but for starters in general what
you want to look for is "spot focus"...  usually iconized
as a square with a dot in the center of it.  Once you've
found and turned it on, center the cat in the viewfinder,
do your half press, then compose your shot.  The cat should
then be perfectly exposed at the expense of the tree.

Hopefully others with your model will be more helpful.

Take care.

Ken

 The Ixus 40, like most P&S cameras, doesn't have the ability to
focus manually.  These cameras usually try to focus on what is
contained in the center of the image (your manual should describe
this).  If the cat was isolated this would be easy.  But as it's
surrounded by the tree, your Ixus 40 is probably going to focus on
some of the much closer leaves and branches.  When you half press
the shutter, the camera not only focuses (and determines the
exposure settings) but it locks them in place.  So if you can find
another object to focus on that is approximately the same distance
as the cat, you could focus on it, and they while keeping the
shutter half-depressed, point the camera back towards the cat, and
then take the picture.  If this other object that you're using to
pre-focus on causes the picture of the cat to come out too light or
too dark, you'll be able to fix that.  One of the Ixus's few manual
controls is exposure compensation, and with that and using an
alternate focus point, you *might* be able to get a nicely focused
picture, assuming that it's not one of those pesky Cheshire's.  :)