Is there a pure CSS way to make an input transparent?

Question

input[type="text"]
{
    background: transparent;
    border: none;
}

Nobody will even know it's there.

I like to do this

input[type="text"]
{
    background: rgba(0, 0, 0, 0);
    border: none;
    outline: none;
}

Setting the outline property to none stops the browser from highlighting the box when the cursor enters

The two methods previously described are not enough today. I personnally use :

input[type="text"]{
    background-color: transparent;
    border: 0px;
    outline: none;
    -webkit-box-shadow: none;
    -moz-box-shadow: none;
    box-shadow: none;
    width:5px;
    color:transparent;
    cursor:default;
}

It also removes the shadow set on some browsers, hide the text that could be input and make the cursor behave as if the input was not there.

You may want to set width to 0px also.

If you want to remove the outline when focused as well try:

input[type="text"],
input[type="text"]:focus   
{
         background: transparent;
         border: none;
         outline-width: 0;
}