Background discrepancy

[#1]

Using Serif WebPlus.  I have a 5 page site with a tartan background - the text and photograph area is white so that the tartan appears on each side of this area.
It is fine on my two laptops (one wide screen, one not) using FF and IE.  At my web class on their desktop it is also OK.  No complaints either from the few folk (friends) who have accessed  it.  I have one friend who can only see the white bit in the middle and can't see the tartan at either side.  She finds this on both of her computers using FF and IE. On one screen capture that she sent me it was totally skew-whiff i.e. the white on one side, the tartan on the other.  I mentioned it to the tutor but didn't get a satisfactory answer. The friend who is seeing this has cleared the cache in the browser. Can anybody help please?

[#2]

Could you attach the screen shot (with any details blanked out, obviously ) - that'd help, though my first thought is what resolution is your friend's screen set to? If it's a smaller resolution it might be that she can't see both tartan sides of the website at the same time?

[#3]

Right, here goes - three snips, first two sent by my pal and the last one is how it should be.  Hope folk aren't too critical of my efforts - 'tis early days and have only been doing it for 3 weeks! 
Thanks for  the interest Matt.