Selecting cell in a spreadsheet by a mouse selects cell several rows below

[kda1998]

It happens in spreadsheet in a Liferay portlet. We have a site header, footer, some other zones, and spreadsheet renders not from the beginning of a page. When you select something by a mouse, selected cell and focus shifts several rows below. It seems to me total sum of the row heights equals to absolute position of the spreadsheet on the screen