The easiest way for images is this:
<div align="center">
<img src="image.gif" width="50" height="50" alt="description" />
</div>
It may not be feasible for many many images, but it works right in the html markup and can be styled accordingly in which ever your preffered method of coding your CSS. For other ways of positioning images, there are the "float:" tags, "background-image:" tags, "position:" tags and so on. These take a bit more knowledge for the correct usage, but offer lots of flexibility.
For centering text, try this:
<!--***********************This is the Doctype--Very important***************************-->
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" />
<link rel="stylesheet" href="3colhf.css" type="text/css" />
<title>Untitled</title>
<style>
<!--
/**************************Here is the head style***********************/
h1 {
color:#ffoooo;
font: bold x-large "Times New Roman", Times, serif;
text-align: center;
}
--></style>
</head>
<body><!--********************Here is the header placed cleanly in the body*****************-->
<h1>SOME HEADER TEXT</h1>
</body>
</html>
First off, get used to adding a doctype if you want search engine and user friendly markup. I myself prefer External Style Sheets, but adding your style in the "Head" of the page is by no means a bad thing, but there are many advantages to useing the styles externally. Text is the easiest and most flexible content type, because there are many ways to manipulate it to flow the way you want.
You could also align it like the image in the first example, but the whole point of CSS is to seperate the content from the layout. Paragraphs can also be styled in this sme fashion as I show in the 2nd example, as well as any other text that is not already in use.
Those are the basics, maybe you can post a link to the page in question or offer a bit of code as AA states above, and Im sure one of us can help you out.
Hope this helps,
nos