A form will not have any functionality in BC unless you create the form in BC. Custom fields and system fields need to match the system ID's generated from those forms to be able to function with the system.
You can grab the html from the forms you make and style, edit and modify the html and css for those as much as you want. (As long as you do not change the ID/Name of the form fields, so again, BC knows where to submit the data to, along with the form action)
Just to clarify something that Liam said, there are no ID attributes (referring to HTML attributes) that matter on BC forms. The attributes that BC looks at are as follows:
- "name" attribute on input, textarea, and select elements
- "action" and "method" attributes on the form element
Adding my 2 cents, just to clarify, a form is HTML it will work anywhere on any system (basically), saving or doing something the data when you submit is another story and Adam and Liam cover that.
Thank you for the help, I probably could have worded my question better, but between the three replies I definitely have my answer