Bonsoir à tous,
Je suis vraiment novice en conception de site et j'ai donc choisi la solution de facilité : prendre pour base un kit graphique.
CELUI-CI http://www.kitsgratuits.com/kit-gratuit/kit-graphique/7.htm
Je précise que ce kit à une bannière flash et visiblement un code en javascript dans le fichier index.html
Je vous ai dit que j'étais novice...rigolez pas 
J'ai donc téléchargé ce kit et l'ai modifié. Je ne l'ai pas encore mis en ligne, il est toujours en phase de conception sur mon PC.
Mon site étant déjà bien avancé, j'ai soumis index.htm au W3C et là... verdict ...13 erreur. Je n'arrive pour l'instant à en régler que 2.
Par curiosité, j'ai donc passé l'index du kit que j'avais téléchargé qui en contient aussi d'origine...
J'ai donc travaillé mon site en lui donnant forme mais là, je coince grave sur les 11 erreurs restantes car visiblement mon site s'ouvre très bien avec Firefox (Chez moi c'est Nickel) mais pas avec IE...
Est c'est là que je coince
Quelqu'un pourrait-il m'aider SVP ? Ca m'aiderai vraiment à avancer. Merci

Validation Output:  11 Errors
  1. Error Line 32, Column 20: Attribute "language" exists, but can not be used for this element.
        <script language="javascript" type="text/javascript">
      You have used the attribute named above in your document, but the document type you are using does not support that attribute for this element. This error is often caused by incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Transitional" document type to get the "target" attribute), or by using vendor proprietary extensions such as "marginheight" (this is usually fixed by using CSS to achieve the desired effect instead).
      This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information.

      How to fix: check the spelling and case of the element and attribute, (Remember XHTML is all lower-case) and/or check that they are both allowed in the chosen document type, and/or use CSS instead of this attribute. If you received this error when using the <embed> element to incorporate flash media in a Web page, see the FAQ item on valid flash.
  2. Error Line 57, Column 5: invalid comment declaration: found name start character outside comment but inside comment declaration
      <!--object,embed{margin:0px!important;}
  3. Info Line 53: comment declaration started here
      ><!--[if IE]>
  4. Error Line 57, Column 6: character data is not allowed here
      <!--object,embed{margin:0px!important;}
      You have used character data somewhere it is not permitted to appear. Mistakes that can cause this error include:
          * putting text directly in the body of the document without wrapping it in a container element (such as a <p>aragraph</p>), or
          * forgetting to quote an attribute value (where characters such as "%" and "/" are common, but cannot appear without surrounding quotes), or
          * using XHTML-style self-closing tags (such as <meta ... />) in HTML 4.01 or earlier. To fix, remove the extra slash ('/') character. For more information about the reasons for this, see Empty elements in SGML, HTML, XML, and XHTML.
  5. Error Line 60, Column 4: "endif" is not a reserved name
      <![endif]-->
  6. Error Line 84, Column 48: NET-enabling start-tag not immediately followed by null end-tag
      …d="logo"><img src="images/logo.gif"/ alt="free flash template logo"><h1><span

      This error may occur when there is a mistake in how a self-closing tag is closed, e.g '.../ >'. The proper syntax is '... />' (note the position of the space).
  7. Error Line 84, Column 48: required attribute "alt" not specified
      …d="logo"><img src="images/logo.gif"/ alt="free flash template logo"><h1><span

      The attribute given above is required for an element that you've used, but you have omitted it. For instance, in most HTML and XHTML document types the "type" attribute is required on the "script" element and the "alt" attribute is required for the "img" element.
      Typical values for type are type="text/css" for <style> and type="text/javascript" for <script>.
  8. Error Line 84, Column 48: end tag for "img" omitted, but OMITTAG NO was specified
      …d="logo"><img src="images/logo.gif"/ alt="free flash template logo"><h1><span
      You may have neglected to close an element, or perhaps you meant to "self-close" an element, that is, ending it with "/>" instead of ">".
  9. Info Line 84, Column 20: start tag was here
         <div id="logo"><img src="images/logo.gif"/ alt="free flash template logo"><
  10. Error Line 57, Column 2: XML Parsing Error: Comment not terminated
      <!--object,embed{margin:0px!important;}
  11. Error Line 60, Column 1: XML Parsing Error: StartTag: invalid element name
      <![endif]-->
  12. Error Line 84, Column 46: XML Parsing Error: attributes construct error
      … id="logo"><img src="images/logo.gif"/ alt="free flash template logo"><h1><sp
  13. Error Line 84, Column 46: XML Parsing Error: Couldn't find end of Start Tag img line 84
      … id="logo"><img src="images/logo.gif"/ alt="free flash template logo"><h1><sp

Au niveau des erreurs :

- Modifie <script language="javascript" type="text/javascript"> en <script type="text/javascript">
- Modifie <img src="images/logo.gif"/ alt="free flash template logo"> en <img src="images/logo.gif" alt="free flash template logo" />

Merci Messieurs de porter de l'intérêt à ma demande.
Je vais essayer dès ce soir car là je retourne au taff et avec 5h de décalage horaire par rapport à la métropole, je peux sembler être long à répondre.
Merci de votre aide.

Voilà ce qu'il me reste.

Validation Output:  5 Errors

  1. Error Line 57, Column 5: invalid comment declaration: found name start character outside comment but inside comment declaration
      <!--object,embed{margin:0px!important;}
  2. Info Line 53: comment declaration started here
    ><!--[if IE]>
  3. Error Line 57, Column 6: character data is not allowed here
      <!--object,embed{margin:0px!important;}
      You have used character data somewhere it is not permitted to appear. Mistakes that can cause this error include:
          * putting text directly in the body of the document without wrapping it in a container element (such as a <p>aragraph</p>), or
          * forgetting to quote an attribute value (where characters such as "%" and "/" are common, but cannot appear without surrounding quotes), or
          * using XHTML-style self-closing tags (such as <meta ... />) in HTML 4.01 or earlier. To fix, remove the extra slash ('/') character. For more information about the reasons for this, see Empty elements in SGML, HTML, XML, and XHTML.
  4. Error Line 60, Column 4: "endif" is not a reserved name
      <![ endif]-->
  5. Error Line 57, Column 2: XML Parsing Error: Comment not terminated
      <!--object,embed{margin:0px!important;}
  6. Error Line 60, Column 1: XML Parsing Error: StartTag: invalid element name
    <![endif]-->

++++++++ Comme le dit Kalliméro, je suis étonné d'apprendre qu'IE serait le cauchemard des concepteurs Web...  j'aurai pas cru ++++++++++

Tout est faisable sur le net maintenant... Regarde sur ce site en haut tu met le lien de ton site et tu choisi dans quel navigateur il doit le lire (IE6,7,8...) et hop c'est magique tu as un screenshot de ton site :p Le lien : http://ipinfo.info/netrenderer/index.php

Et ils en existe d'autres : 7-outils-pour-tester-vos-sites-sur-tous-les-navigateurs