Dreamweaver 's problems (20ps)

Don't know why I select a image to be the background, i can see the background in Dreamweaver but the webpage backgroung is blank.
My background step:
1)Modify->Page Proportise->Background image->select the image
->Apply->OK
What's the problem of it?? Thanks!!
---
I set the webpage name in Dreamweaver but the name in webpage is
Untitled Document.
My step:
Input the name in each page tiltle.
---
Please help , thank you very much!!!