If you read all the validation explainations the valdiator gives, you can see whats wrong:
…href="#" id="M1"><div class="alignment">RESTURANT<br />EQUIPMENT</div></a></li>✉
The mentioned element is not allowed to appear in the context in which you've placed it; the other mentioned elements are the only ones that are both allowed there and can contain the element mentioned. This might mean that you need a containing element, or possibly that you've forgotten to close a previous element.
One possible cause for this message is that you have attempted to put a block-level element (such as "<p>" or "<table>") inside an inline element (such as "<a>", "<span>", or "<font>").
You cant place a block level element within an inline element.
You also dont have an opeing and closing <ul></ul> tag.
Unless you left them out here in your post.
Now what exactly do you mean by double line menu? Do you mean Drop Down? if so there are many many tutorials to create CSS based DD menus online.