You need to use CSS to accomplish this. I usually do an inline style on my items like this:
For Text Boxes
<input type="text" name="text1" style="width:200px;">
For Drop Down Menus
<select name="select1" style="width:200px;"></select>
The result are text boxes and drop down menus that are 200px wide. And for the record this should be posted in the Client Side Technologies forum 🙂