body {
    counter-reset: thm;
    background-image: url("bg.jpg");
}
h1 {
	text-align: center;
}
h2 {
  font-weight: bold;
  background-color: lavender;
  padding: .2em .5em;
  margin-top: 1.5em;
  border-top: 3px solid #666666;
  border-bottom: 2px solid #999999;
}

#wrapper {
    margin-left:auto;
    margin-right:auto;
    width:1000px;
}

.blockhl {
	border: 1px solid black;
	background-color: #F0F8FF;
    margin-left: 5em;
    margin-right: 5em;
    padding-left: 0.5em;
    padding-right: 0.5em;
}



section {
    width:1000px;
}


table {
    margin-left: auto;
    margin-right: auto;
    text-align: center;
    border-collapse:collapse;
    border-spacing: 20px 50px;
}

table td {
    border-right: 1px solid #000;
    border-left: 1px solid #000;
}

table thead td { 
    border-bottom: 1px solid #000; 
}

/* navigation */

nav {
    list-style-type: none;
    line-height:30px;
    height:20px;
    width:170px;
    padding-top: 120px;
/*    margin-left: 850px;*/
    position: fixed;
}


nav a:link, 
nav a:visited {
    line-height:30px;
    display: block;
    width: 110px;
    font-family: serif;
    color: black;
    background-color: lavender;
    text-align: center;
    padding: 5px;
    text-decoration: none;
}

nav a:hover, 
nav a:active {
    background-color: white;
}



/* theorem style*/
.theorem {
    display: block;
/*    margin: 12px 0;*/
    font-style: italic;
}
.theorem:before {
    counter-increment: thm;
    content: "Theorem " counter(thm) " ";
    font-weight: bold;
    font-style: normal;
    
}

.lemma {
    display: block;
/*    margin: 12px 0;*/
    font-style: italic;
}
.lemma:before {
    content: "Lemma.";
    font-weight: bold;
    font-style: normal;
}
.proof {
    display: block;
/*    margin: 12px 0;*/
    font-style: normal;
}
.proof:before {
    content: "Proof.";
    font-style: italic;
}
.proof:after {
    content: "\25FC";
    float:right;
}
.definition {
    display: block;
/*    margin: 12px 0;*/
    font-style: normal;
}
.definition:before {
    content: "Definition.";
    font-weight: bold;
    font-style: normal;
}