Error Line 150, column 51: there is no attribute "name" .
<form method="post" action="connection.php" name="formulaire">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.

&#9993;

Error Line 161, column 9: element "SCRIPT" undefined .
<SCRIPT>document.formulaire.pseudo.focus();</SCRIPT> You have used the element named above in your document, but the document type you are using does not define an element of that name. 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 "Frameset" document type to get the "<frameset>" element),
by using vendor proprietary extensions such as "<spacer>" or "<marquee>" (this is usually fixed by using CSS to achieve the desired effect instead).
by using upper-case tags in XHTML (in XHTML attributes and elements must be all lower-case.

<form method="post" action="connection.php" name="formulaire">
<div><label for="pseudo">Pseudo : </label><input type="text" maxlength="20" name="pseudo" id="pseudo"/>
<br/></div>

<div><label for="password">Password : </label><input type="password" name="password" id="password"/>
<br/></div>

<div><label for="remember">Se souvenir de moi ? </label><input type="checkbox" name="remember" id="remember"/>
<br/><br/></div>
<div><input type="submit" value="Connection"/></div>
</form>
<SCRIPT>document.formulaire.pseudo.focus();</SCRIPT>

Quelqu'un peut m'aider ???

<script type="text/javascript"></script>

<script language="JavaScript" type="text/javascript">
// Ton code par là
</script>