Changing keyword search box size

By default, Zen Cart's keyword search box at the header is configured to display with 100 pixels wide. The default will also limit customer’s keywords to 30 characters. To change the default you must edit the following file:
...\includes\templates\template_default\sideboxes\tpl_search_header.php

Note: if you are using another template you should replace “template_default” with the name of your template.

All you need to do is to edit the two function calls to zen_draw_input_field(...).

Change the parameter maxlength=30 to any number of characters you want to give users more space for keywords.
To change the size of your search box you need to edit the style="width: 100px". Resize the text box according to the requirements of your design.