Tabbing doesn't scroll the page up if the control underneath the first screenfull is a dropdownlist

I have made a web form which spans approx 3 pages lengthwise. Tabbing from one field to another is ok upto the last control on the first screenfull . However after that there is a dropdownlist and tabbing from the last control of the first screen to the dropdownlist doesn't make the page scroll down automatically and the focus is lost if i manually scroll down. Seems to be a peculiar problem and this problem does not exist if there is a textbox instead of a dropdownlist on top of the second screen .

Please help

Regards

Sanjish
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