I use Windows Live Hotmail “Full Version” and in “Full Message View”, ie. with the Reading Pane off, so I’m not sure if the same problem occurs if the reading pane is on. The solution that I have found to this problem with Firefox and Windows Live Hotmail is quite simple and just involves installing a Free Extension or Add-on for Mozilla Firefox.

The extension is called Stylish and can be downloaded from the link below.

https://addons.mozilla.org/en-US/firefox/addon/2108

Once you have downloaded and installed the Add-on, you will have to restart Firefox. After restarting, you will see a new icon near the bottom-right side of your Firefox window. The icon looks like this

Open Windows Live Hotmail and then right click the Stylish icon. From the menu that comes up choose Write Style > For mail.live.com

In the new window that pops up, enter the following:

Here is the code for easy selection. Just select it, copy and paste.

@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document domain(“mail.live.com”) {
.ReadMessagePane {overflow-y:scroll !important; overflow-x:scroll !important}

}

The Description could be anything you want actually, but I’ve use the description above as it most suits the situation. Click Save when you are finished entering the information above and scroll through some images. There should not be any more of those pesky lines.