By using the Data URI scheme you can embed images directly into your HTML and CSS. It works by encoding an image into a base64 string and place it directly withing an HTML image tag or as a CSS background URL. Such a base64 string url example in your CSS looks like this:

div.image {
 background: data:image/x-png;base64,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
}

I found this generator who generates such a string after uploading an image.
I used this for iPhone/iPad app development.

http://webcodertools.com/imagetobase64converter

Then this is your .htaccess file content. (Do not forget the [R=301,L] or it won’t work)

RewriteEngine On
# first make sure my www is not touched
RewriteCond %{HTTP_HOST} !^www.mydomain.com
# the subdomain you want to create
RewriteCond %{HTTP_HOST} ^forum.mydomain.com
# the place to redirect to
RewriteRule (.*) http://www.mydomain.com/forum/?option=com_kunena&Itemid=0 [R=301,L]

1. Get rid of the image flickering. This is what happens when using roll-overs for multiple images, both images will be requested from the server. Although the time is pretty fast, you’ll will see the image flickering
2. Reduce page requests – One big image might be heavier to download, nowadays it will be faster and directly loaded in your page then requesting multiple images

There are some handy Firefox tools, which you can use for website performance optimization:
Live HTTP Headers and Firebug.
Within Firebug, you can select the NET tab. From here you can see all the requests to images.

See the sprites which are used for Amazon, YouTube or even for Google.

There are even online tools for generating these sprites, so you don’t need Photoshop for calculating.

How to implement it? – Just by smart using the background property.
For example:

#navigation {
 width: 500px;
 height: 20px;
 overflow: hidden; //no image outside the defined clipping area is visible
}

#navigation a {
 display: block;
 width: 100px;
 height: 20px;
 text-indent: -10000px; //for removing the link text off the screen
 background-image: url(sprite.png) //link to your sprite image;
}

#nav-home a { background-position: 0 0; //position of sprite x y }
#nav-home a:hover { background-position: 0 100px; //note the changed y-position }
#nav-about a { background-position: 20px 0; }
#nav-about a:hover { background-position: 20px 100px;}

You can put everything in your sprite, think about icons, backgrounds, borders and corners.
It’s even possible to combine it with background repeating.

Some computer software contain social security number (sofi nummer) checks for making sure that the user fills in the correct social security number. The social security number can be tested by a similar 11-digit-check, which is used a lot for testing electronic payment transfers (on 9 and 10 digit bank account numbers), to check if they are valid.

The 11-digit-check multiplies every number with it’s position, adds these numbers up and divides the result by 11. The result should be > 0.

For example, bank account number: 73.61.60.221 can be calculated:

   (7 ×9 + 3 ×8 + 6 ×7 + 1 ×6 + 6 ×5 + 0 ×4 + 2 ×3 + 2 ×2 + 1 ×1) / 11 = 16

For social security numbers the formula is a bit different.
The last number will be multiplied by position -1 instead of 1.

Now of course tools like this do already exist:
Check the following URL:
http://www.wilmans.com/sofinummer/index.html