One of my users asked if there was a plugin to take automatically a screenshot from a submitted website url. He also asked if there was a wordpress plugin for this.
can anyone tell me if such a plugin exist for wordpress or if it's possible with php, ajax or any other language?
I personally don't know of any Wordpress plugins that take screenshots of a submitted website url, however there is a very nice service at http://browsershots.org/ that might be what you're looking for. Browsershots will render screenshots in almost any combination of browser and OS you could ever want.
Hope this helps.
As far as I understand your question you can use http://wordpress.org/extend/plugins/seekxl-snapr/ this plug-in will show a thumbnail of the url as the mouse over.
There are other plug-ins that uses websnapr[dot]com to create the images as well.