The use of style sheets gives many advantages to the HTML writers: style sheets provide a richer page layout; the same style sheet can be shared by several documents, which allows to gain much time by the writing of HTML code; they improve the site's coherence. Indeed, the website designer will not have to check the homogeneity of his site (this is particurlarly true for sites, which are created by a team). Information of one kind (like headings of the same level, paragraphs, etc.) will automatically be presented on the same way without any constraint of systematically repeating the same layout elements.
Moreover, style sheets help to improve the accessibility of a document. A most used technique consists in changing the structuring elements from the original purpose to format a paragraph (like for example the use of a «DL» element to set a margin). Style sheets help to do the same thing with more precision in an accessible way. Another technique consists in using a picture to replace a title. If this picture is not commented, the document becomes completely inaccessible. In this case also, style sheets can be used (the website designer will gain much time and the quantity of documents to be downloaded by the user will be considerably reduced).
Each browser can use or not use the layout indications (character size, fonts, styles and so on.). As far as software for blind and partially sighted users are concerned, these indications are often useless. Just ensure that the documents can be used by a browser that does not support those style sheets (to that extend you either just have to place the style sheet in a «.css» file or to write the styles in a comment at the beginning of the document).
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