ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  width: 200px;
  
}

li a {
  display: block;
  color: #000;
  
  padding: 6px 16px;
  text-decoration: none;
}

/* Change the link color on hover */
li a:hover {
  background-color: #555;
  color: white;
}

.articalol
{
width: 50%;

}


.articalol ol {
  list-style-type: none;
  margin: 0;
  padding: 0;
  width: 50%;
  background-color: lawngreen;
}

.articalol li a:hover {
  background-color:lightgreen;
  color: white;
  font-style: oblique;
  color: darkblue;
}
.articalol li a {
  display: block;
  color: #000;
  
  padding: 6px 16px;
  text-decoration: none;
}
@media (max-width: 600px) {ul, .articalol, .articalol li a ,.articalol li a:hover, .articalol ol, li a
  {
    width: 100%;
    height: auto;
align-content: center;
text-align: center;
  }
}
<style>
ul.mainblock {
   list-style-type: none;
 width: 70%;
  
}

ul.mainblock li{
  display: block;
  color: #000;
  
  padding: 6px 16px;
  text-decoration: none;
}


.mainblockcss {
  display: block;
  color: red;
  
  padding: 6px 16px;
  text-decoration: none;
}


.mainblockh3 {
  display: block;
  color: blue;
  width: 90%;
  padding: 2px 10px;
  text-decoration: none;
}

.mainblocktxt{
  display: block;
  padding: 6px 16px;
  text-decoration: none;
}

.mainblocklink{
  display: block;
  color: blue;
    padding: 6px 16px;
  text-decoration: none;
font: italic;
}

.mainblocklink:hover {
	text-decoration: underline;
}

/* Change the link color on hover */
li.mainblock a:hover {
  background-color: #555;
  color: white;
}

ol.mainblock  {
  background: #ff9999;
  padding: 20px;
}


ol.mainblock  li {
  background: #ffe5e5;
  padding: 5px;
  margin-left: 35px;
  
}

.imgposition{
text-align:center;
vertical-align: middle; 
width: 100%;
padding-top: 5%;
padding-bottom: 5%;
border:1;
}

</style>