<head>
<title> Test Page </title>
<style type="text/css">
h1{
color:white;
}
img{
float:right;
}
</style>
</head>
An internal stylesheet is an embedding of CSS code into an individual webpage, effecting only that page. It can only be placed in the head. If you want to effect more than one page, you will need an external stylesheet. You need to use a <style> element to let the browser know that code is actually CSS; don't forget to include the text attribute with the value of "text/css", though it would likely work without it. See Parts of a CSS Rule for how to construct a rule.
Incidentally, if you forget the closing style tag it will probably eat the whole page (treat the rest of the page as CSS). Just watch out for that or always create the closing tag when you write the opening one.