This is old news for most of us and yet when I wanted to quickly find it, it took some searching. So here it is, in simple language, what you can do to prevent your web pages from being cached by browsers.

Add in your head section (between and tags):



And then add the same code just before the ending tag:



Explanation:
The Pragma directive is to satisfy most browsers. However Internet Explorer doesn't work with it at the beginning, so we have to place it at the end too. Again IE 5.5 doesn't recognize it. So we need to add the Expires directive too. Hat tip

Note: In WordPress you can call the function nocache_headers() to prevent caching by modifying HTTP headers, as dicussed in the comments below.