HTML validation error....

I am using views slideshow 6.x-1.0-beta2 version ,i have placed the slideshow on the front page it consists of image & its respective teaser, it works absolutely fine.The problem is while validating (i.e w3schools validate local HTML) i get an error:

Line 148, Column 428: Attribute "alt" exists, but can not be used for this element.

…p;quot;311" />" alt="<img src="http://www.ven

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 element to incorporate flash media in a Web page, see the FAQ item on valid flash.

Also my default DOCTYPE is 'strict' .... and would want it to remain 'strict'.On viewing the page source I found out that it is due to the views slideshow ...!!