This is my custom.css file in: ~/.ipython/profile_customcss/static/css/custom.css

gistfile1.css

/**write your css in here**/
/* like */

<style>
    .CodeMirror{
        font-family: "Consolas", sans-serif;
    }
    
pre, code, kbd, samp {
     font-family: Consolas, monospace;
}

	div.input{
	width: 105ex;
}

div.text_cell{
	width: 105ex;
}

div.text_cell_render{
	width: 105ex;
}

    div.cell{
        max-width:750px;
        margin-left:auto;
        margin-right:auto;
    }

    h1 {
        text-align:left;
    }