Compressing Jpegs on mac OSX

I have just recently purchased my mac computer, and need help to compress my photo for the web. I have been using window up untill this point, but obviously mac has a different way of doing this process can some one help me.

What kind of photos are you talking about and what file format are they in? If you have a new Mac, it should have a program included called "Preview". You may be able to trim your photos with it.

JPEG files are already heavily compressed, and re-compressing them will just lose more image data and reduce the quality.

About all you can do is reduce the size dimensions and make sure its 72dpi (if it's higher, reduce it to 72 for web use).