“view site” option in dashboard

I have discovered something that puzzles me as a newbie. When you make a design change to your template in the admin application like adding links or posting, you can see how it affects the appearance of your blog by clicking on the <view site> hypertext at the top of the page in dashboard and in other places.

However, when you change a template graphic – like substituting personalheader.jpg for the header art that is named in the style sheets, or even if you edit or rename the the original art, you do not see changes in your blog’s appearance when you view the site you are trying to create. What is generating the view? I have sometimes made changes that caused the header art to disappear altogether, but I’ve never been able to have the <view site> function display a changed or replaced graphic. The template graphic is the only thing that shows – even if the file called for in the style sheet is not even in the directory annymore!

What’s up? How can I see changes I’m trying to make in header art? I’m doing my design work on my PC under XAMPP.

Thanks

What