How do I make a picture smaller?

[Vinjuhh]

When I post an image in a thread it's EXTREMELY LARGE Lol. How can I make it smaller?

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EXAMPLE

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[Zoefken]

http://www.bricelam.net/ImageResizer/

 

[EpicNPC]

Images are automatically resized there, so even if you post a big image a smaller image will appear in your thread.