I am no expert but don't forget the maps are Ordnance Survey copyright licensed to Memory Map.
When I asked about this the reply from OS was difficult to follow and subsequently I contacted a couple of walking websites that display OS maps. Their advice was that they have a 'Paper Copying Licence' from Ordnance Survey at about £60 per year.
It depends what your website is used for.
If it is purely for information and you make no money out of your website you can possibly look at getting a Paper Copying Licence from the OS. They are renewable on an annual basis and cost about £60 (in 2010).
However you need to check that the way you want to use the map is allowed using that licence.
Two points the rules actually state is that it has to be a copy of a paper map and not an image from Memory Map, you are also meant to put a watermark across the map, presumably to make sure people can't print out virgin copies.
Alternatively you could always use the OS Open Space Web builder route where you can add markers and routes to OS maps - see http://www.derbyshireheritage.co.uk/Menu/map.php
for an example of a static map. You can sign up for free at http://www.ordnancesurvey.co.uk/oswebsi ... i/wmb.html
. The builder supplies the necessary code to include on a website - the number of tiles is limited but I would say they give plenty for normal use.
You could also use Google maps to put your routes on to display on a website.
Both OS Open Space and Google options can be written into your website pages legally.
On the other hand if you use Wordpress for a CMS or blog then there a plugins for both of these options.
Having said all that I know of at least one site where they just take pot luck and put copies of whatever they like on the net.
At the end of the day it's a bit of a minefield.