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: 
Another trick would be to have two img tags, and hide one depending on the device. 

HTML

```
<img id="img1" src="images/arts/IMG_1447.png" alt="">
<img id="img2" src="images/arts/IMG_1447m.png" alt="">

```

CSS

```
#img1 {display:block;}
#img2 {display:none}

@media all and (max-width: 499px) {
    #img1 {display: none;}
    #img2 {display: block;}
}

```
you can't change an image source like that. You'll need to use a div with the original as a background image for this to work.

```
<div id="ifMobile1" style="background-image: url(images/arts/IMG_1447m.png);"></div>

```