If you absolutely have some uncontrollable urge to use hot-linked images:
»How wide can an uploaded graphic be?
Using Image Tags for Linking Off-Site
Any graphic wider than 700 pixels linked off-site using [img] tags will not be resized, and it will blow out the right margin of the posting window. The extended margin will affect the entire posting page, and it can render the thread difficult for you and others to read. If this occurs, mods will edit the graphic to include a "width" statement, changing the graphic size. Please be considerate of others when posting images.
Otherwise, try this:
»How do I post attachments and screenshots?
»Inline Images in Posts
Not all of us have 36" 1920 x 1600 (or larger) monitors. --
A well-regulated militia, being necessary to the security of a free State, the right of the people to keep and bear arms shall not be infringed.