First you need to figure out what part of the page is taking up the space.
I would recommend inspecting the page in a web browser. Using this tool, you can tell what part of the page is taking up the space. You can also use this tool to see what part of the element is taking up the space(padding/margin/border). It is likely the body or a child of the body. To remove the space, you will need to set a style rule. You can do this multiple ways. The simplest and least pretty way is to do an inline style. Try this inside the tag for the element that is taking up the space:
style="padding:0px;"
In the tag, it will look like
<body style="padding:0px;">
If this padding does not work, try other properties of the element(margin/border/width). You will need to fine tune this to look exactly the way you want it