CSS Dropdown menu for the header- With Categories!

[gee38l]

It seems i am having an issue as stated above with the css header going all wack when the screen is resized to about 800x600 resolution. It moves the menu to the right (see attached pic) and also pic above from CES .

Here is my current css:

div#dropMenu {
	width:auto;
	margin:0px;
    text-align:center;
	z-index:1000;
        position:absolute;
        top:198px;
        bottom:300px;
        left:200px;
        right:0px;
         width:865px;

Anyone know why its moving to the right on smaller screen and also when you resize the screen?