<img /> tags need alternative content with "alt" attribute. "dots.png" is not a content. Using CSS backgrounds instead.

"border" attribute is not a valid attribute for <img /> tags. Using proper CSS instructions instead.

<br /> is not a valid strict xhtml1.0 tag. Not semantic. Replacing it by CSS instructions on semantic tags.

center is not a valid strict xhtml1.0 tag (not semantic). At least, replacing it by a div with "center" class.