UPDATED: 21 January 2012

To make your website secure and safe read this article How to create java website secure and safe?

I'll give you some tips to do it and you can see the effect its loading way much faster. Some content you ignored but it really matters when user have slow connection speed. Let me show how you made your site and its old idea to do it. Your site currently having this scenario as below.
This is how your site works if you didn't optimized it. Now we'll see how you can optimize if you didn't. Check your site grade using Yslow http://developer.yahoo.com/yslow/ We'll do optimization and after that check your grade you'll see it increased.

Compress StyleSheet, javaScripts
You must compress content to make response faster. So it'll take less time to load. Removing whitespace, unwanted semi colons from the StyleeSheet, javaScript. Use the below online tool to compress it

• StyleeSheet (CSS) - Tool compress css and give you compressed CSS. Compress CSS in .css file as well as data between <style></style>
• Tool : http://www.csscompressor.com/
• Note: This tool compress CSS but some time it made changes according standard CSS rules. If you made any tricks in CSS it'll be omitted. After compression test your CSS and make changes again  for tricky CSS

Compress images, Don't scale it.
Compress images using some software, or online so it load faster on client side. Below some sites that helps you to convert and compress images. Secondly don't scale images say image 128x128 and you try to show as a 30x30. Better to make that image 30x30 rather then showing 128x128 image using width = 30.

• .png : http://images.my-addr.com/resize_png_online_tool-free_png_resizer_for_web.php
• .jpg : imageoptimizer.net

Few HTTP request

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.http.HttpServletResponse;

public class cacheControl implements javax.servlet.Filter {
    FilterConfig filterConfig = null;

    public void init(FilterConfig filterConfig) {
        this.filterConfig = filterConfig;
    }
    public void doFilter(ServletRequest req,
            ServletResponse res,
            FilterChain chain)
            throws IOException, ServletException {
        String sCache = filterConfig.getInitParameter("cache");

        if (sCache != null) {
            ((HttpServletResponse) res).setHeader("Cache-Control", sCache);
        }
        chain.doFilter(req, res);
    }
    public void destroy() {
        this.filterConfig = null;
    }
}

Create servlet using above code. Make an entry in web.xml if you are not using some IDE. Now set filer for what you want to set expiry header. Like *.css, *.js, *.png, etc....Copy paste the below code in web.xml . *.css, *.js, means every css from your domain, Below code have max-age=250000 mean it'll store data round about two days. You can also append *.png, *.jpg, etc... create proper filter.

<filter>
        <filter-name>Cache</filter-name>
        <filter-class>alien.config.cacheControl</filter-class>
        <init-param>
            <param-name>cache</param-name>
            <param-value>public, max-age=250000</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>Cache</filter-name>
        <url-pattern>*.css</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>Cache</filter-name>
        <url-pattern>*.js</url-pattern>
    </filter-mapping>

compression="on"
compressionMinSize="2048"
noCompressionUserAgents="gozilla, traviata"
compressableMimeType="text/html,text/xml,text/plain,text/javascript,text/css"

<Connector URIEncoding="utf-8" connectionTimeout="20000" port="8084" protocol="HTTP/1.1" redirectPort="8443" compression="on" compressionMinSize="2048" noCompressionUserAgents="gozilla, traviata" compressableMimeType="text/html,text/xml,text/plain,text/javascript,text/css"/>