Although an InDesign default text input field appears to have no border or background when added to a layout,

Screenshot of text and default input text field on a cyan background with 40% tint in InDesign


it is exported with in5 with a white background and a border.

Screenshot of in5-exported text and default input text field on a cyan background with 40% tint in Chrome where the input text field has a white background and a rounded gray border


You can modify the appearance of the exported text input fields by adding CSS in the Resources section of the Export HTML5 with in5 dialog (in5 > Export HTML5 with in5... or in5 > Easy Export Wizard... and click the Advanced button). The following CSS snippets can be used to modify the appearance of the exported text input field.



Remove the white but keep the border 

If you'd like to remove the white but keep a border, 

Screenshot of in5-exported text and default input text field on a cyan background with 40% tint in Chrome where the input text field has no background and a beveled gray border


then copy the following CSS and add it in the Resources section of the Export HTML5 with in5 dialog (in5 > Export HTML5 with in5...):

input,select,textarea { 
    font-size:inherit; 
    background-color: transparent; 
}



Remove both the white fill and the border 

If you'd like to remove both the white fill and the border, 

Screenshot of in5-exported text and default input text field on gray background in Chrome where the input text field has no background and numbers have been entered to show the location of the input text field


then copy the following CSS and add it in the Resources section:

input,select,textarea { 
    font-size:inherit; 
    background-color: transparent; 
    border-color: transparent;
}



Remove both the white fill and the border and add the spacing between characters 


If you'd like to remove both the white fill and the border and add spacing between characters,

Screenshot of in5-exported text and default input text field on a cyan background with 40% tint in Chrome where the input text field has no background and numbers have been entered to show the location of the input text field

then copy the following CSS and add it in the Resources section:
input,select,textarea {
    font-size: inherit;
    background-color: transparent;
    border-color: transparent;
    letter-spacing: .3em;
}

You can change the value of the letter-spacing attribute to increase or decrease the spacing.