A lot of Web page editing software add to the HTML code proper so-called "extensions", i.e. pseudo-HTML commands that produce special aesthetical effects but can be interpreted by some browsers only (usually the one also sold by the same company as the Web page editor). As a result, too many Web pages can be properly accessed only by using a given version (or another) of a given browser (or another). The author of the present pages (J. Le Fèvre) fully supports the "best viewed with any browser" campaign, according to which Web pages should be accessible in the same way to all browsers (or at least to all commonly used ones). The code in the present pages was directly written with a text editor and does not include any instruction (such as Javascript or Java applets) that is not part of HTML proper. The pages were submitted to the validation service of W3C, the consortium officially in charge of regulating the HTML norm. They were corrected for any errors found by this service and were transferred to the site only once recognised in full conformity with the "HTML 4.0 Transitional" norm. This version of HTML was chosen because it offers many more lay-out instructions than previous versions, while being easily interpreted by (nearly) all browsers available since the beginning of the 1990s. In the "HTML 4.0 Strict" norm, which should in theory be preferred, most lay-out codes are no longer recognised and they are replaced with "style sheets" that some browsers still widely used cannot interpret.

It is otherwise generally desirable to restrict the size of files accessed through Web pages, especially as regards graphics (about 30 Kb is a reasonable limit), in order to save bandwidth and minimize download time. This rule unfortunately cannot be complied with for the present site, which, among other purposes, has to provide full access to unaltered images. Despite the GIF compression, some SeaWifs mosaic files, for instance, are well in excess of 100 Kb. They have to be retained as they were obtained, with the drawback that their download to some users may be irritatingly sluggish.