Take a look at

http://rainsongmanchesters.internet/news.htm

and spot the black strip over the header image.

Now click the link http://rainsongmanchesters.internet/breedinfo.htm

and notice how there's no strip. This type of simple problem? It's defeated me for several weeks! Using firebug, and merely looking in the code for several weeks hasn't created any solutions. Help!

you've got a < br /> within the header (line 16 from the source)

Try getting rid of the additional break (< br />) towards the top of the page.