I have this line of code:
<input type="submit" class="submit" name="submit" id="searchsubmit" value="<?php esc_attr_e( 'Search Products', 'paralinx' ); ?>" />
:before
and :after
are only available on elements that can have content
in between an opening and a closing tag. <input type=submit>
cannot have content.
Use
<button type="submit" class="submit" name="submit" id="searchsubmit"><?php esc_attr_e( 'Search Products', 'paralinx' ); ?></button>
instead, it does allow the usage of :before
.