The items in the standard categories listing are floated left; your stylesheet has apparently removed this.
Code:
.centeredContent, TH, #cartEmptyText, #cartBoxGVButton, #cartBoxEmpty, #cartBoxVoucherBalance, #navCatTabsWrapper, #navEZPageNextPrev, #bannerOne, #bannerTwo, #bannerThree, #bannerFour, #bannerFive, #bannerSix, #siteinfoCredits, #siteinfoStatus, #siteinfoIP, .center, .cartRemoveItemDisplay, .cartQuantityUpdate, .cartQuantity, .cartTotalsDisplay, #cartBoxGVBalance, .accountQuantityDisplay, .ratingRow, LABEL#textAreaReviews, #productMainImage, #reviewsInfoDefaultProductImage, #productReviewsDefaultProductImage, #reviewWriteMainImage, .specialsListBoxContents, .categoryListBoxContents, .additionalImages, .centerBoxContentsSpecials, .centerBoxContentsAlsoPurch, .centerBoxContentsFeatured, .centerBoxContentsNew, .gvBal, .attribImg {
text-align: left;
}
That may have been to make one of the many other elements grouped with it stop floating and align vertically... only the one who did it knows.