Screen.height and Screen.width Issues

I have several type of windows that use Screen.width and Screen.height. Some reason the Width of the Screen keeps going off the screen by a couple hundred pixels. I was wondering if this would be a program fault or engine fault.

ChatWindowSize  = new Rect(0,Screen.height/2,Screen.width/3,Screen.height);

but Screen.height just goes beyond my window space and have to subtract about 300 to get it back on to screen. Same goes for Screen.width.
I have tryed building and running it at a higher resolution. Still the window goes off the screen.

Take a close look at the parameter of a Rect(). They are (x,y,width,height). So you are placing your window half way down the screen with a full screen of height, so the bottom 1/2 will be cutoff.