If you are trying to get your map into MS Word or PowerPoint, usually the EMF format is best. EMF files generally look the same as what you see on the screen and are quite small in size, so they generally work the best. You can either try copying the map from MapViewer with the Home | Clipboard | Copy All Layers command and pasting directly into Word or PowerPoint, or you can export the map to an EMF file and insert the EMF into Word.
Other image formats (JPG, PNG, TIF) may work as well if the exported file is high enough resolution (e.g. 300 dpi), but then the file size of the image (and hence the Word/PowerPoint document) could become very large.
Updated October 3, 2016