How to fit a background image in html without it repeating to cover the whole page? Is there a HTML code for it or do I have to use a CSS code?
The best solution for your question is adding background-repeat:no-repeat or background-size: cover to your CSS or your element's style tag.
For example:
html { 
   background: url(images/bg.jpg) no-repeat center center fixed; 
   -webkit-background-size: cover;
   -moz-background-size: cover;
   -o-background-size: cover;
   background-size: cover;
}
If you insist on using HTML only, you would have to resize the element according to your image, or the other way around. Your question refers to a page's background image, so for my openion CSS or style is the only way to achieve this.