Illustrator: save a slice as PNG

I don’t usually use illustrator to slice the images. Photoshop is better at that, but I use Illustrator to do all my web design work.

The best way to export to the web is to separate out the elements and put artboards around them (shift+O). You can then export those artboards to the web using save for web (command+option+shift+s). With save for web you can modify the format you’re exporting and the settings associated with those formats.

Just remember, to ensure your images have nice, clean lines you should select them and make sure their position (top left corner) is on an even number, not a decimal. This will ensure that you get a solid line when you save for web.

I hope that helps!