I'm making a wiki using Mediawiki. I've seen a right side bar of each page on other wikis. Like this: http://minecraft.gamepedia.com/Diamond_Ore
The right side bar has information about the thing that the wiki post explains or what ever.
I want to know if it's possible to make that on each page, and how?
Wikipedia Infoboxes are just tables with a right side float and some additional style, colors, etc.
Here a minimal example floating table with 1 column (and 1 row):
{| style="float:right; border:1px solid black"
| My fantastic infobox
|-
| More info
|}
To understand that syntax, read the official documentation:
https://www.mediawiki.org/wiki/Help:Tables
You may be surprised that, this is just a table with two columns and some rows:
Here the code:
{| style="float:right;border:1px solid black"
!colspan="2" | Fantastic Page
|-
!colspan="2" | [[File:Example image.svg|260px]]
|-
! Info
| Stuff
|-
! More Info
| More Stuff
|-
! And Info
| Again Stuff
|}
Useful extra information:
Note: this is OK for the presentational side, but for the content side one should also carefully think where to store the actual data. Especially if you want to create a wiki farm. Possibilities include standard wikitext/template syntax, SemanticMediaWiki, Wikibase.