Question: Do Perl, Python or Ruby run flawless on a 64bit Win7 system, or do you have to keep in mind pitfalls with integers and restriction on functions like I have read of on PHP?

Answer: 
If you want to live in the future, the `<picture>` element is the way to go. It still has really bad browser support (only blink based browsers, and firefox beta as of now). The good news is that it falls back to a dumb `<img>` tag, so no harm done except a little slower loading if it's not supported.

### Alright, so how does it work?

*Most of this example is taken from [html5rocks](http://www.html5rocks.com/en/tutorials/responsive/picture-element/) with some modifications*

A picture element looks like this:

```
<picture>
  <source 
    media="(min-width: 650px)"
    srcset="images/kitten-stretching.png">
  <source 
    media="(min-width: 465px)"
    srcset="images/kitten-sitting.png">
  <img 
    src="images/kitten-curled.png" 
    alt="a cute kitten">
</picture>

```

Try the example for yourself at <http://googlechrome.github.io/samples/picture-element/>, simply resize the width of the browser to see the kitten change.

The cool thing about the picture element is that it allows you to specify media queries to each of the `<source>` elements. The last `<img>` is shown if no `source` is matched, or if the picture element is unsupported.
Updated: Please have a look at <http://jsfiddle.net/p96denv4/2/>

Here's what you would do. 

HTML

```
<div id="ifMobile1"></div>

```

CSS

```
#ifMobile1 {
    background-image: url(/images/arts/IMG_1447m.png)
    width: set your width  ;
    height: set your height  ;
}

@media all and (max-width: 499px) {
    #ifMobile1 {
        background-image: url(/images/arts/IMG_1447.png)
        width: set your width  ;
        height: set your height  ;
    }
}

```