Hard maths

Today I decided to try and take some pictures for my millinery website... I have to admit that website building is way outside my comfort zone, even though I am using a ''customisable template''.  I needed a picture for the front page, and read the instructions on pixel size,  then did some ratios, measured with a ruler, and then took several photographs in different size formats, being pretty sure that one would almost work... Well, I think my maths must have been wrong somewhere along the line,  as none were particularly successful.... I think the ones I tried just by pointing and clicking and judging by eye were the most successful....  The above picture is the right width, but need to be cropped by a third in height....  It is a somewhat long and thin space - I have a picture which works perfectly in the gap,  a panorama of the Sydney Opera House and Harbour Bridge, so unfortunately not hat related.! 
I see a lot more trial and error ahead