f7723559_CSS_HTML_XHTML_Reference_Book__Description_and_notes
[Property/Values] vertical-align either baseline, sub, super, top, text-top, middle, bottom, text-bottom, a percentage, a length, or inherit [Description and notes] 
for aligning elements vertically initial value: baseline; may only be applied to inline-level and table cell elements; not inherited; percentages refer to the element's line-height property
CSS HTML XHTML Reference Book
Description and notes