Here is my problem:
in css
table{
    position:absolute;
    top:-100px;
    left:90px;
    margin:300px;
    background-color:#000000;
    a:link {text-decoration:none;}
    a:visited {text-decoration:none;}
    a:hover {background-color:Green;}
    a:active {text-decoration:underline;}
}
{ mark which is next to table is closed by } mark that the end of a:link {text-decoration:none;} and opening brace mark { which is right next to a:link and closing brace mark } at the bottom are becoming useless. 
How can I connect that first and last { } marks with each other ? (not with that a:link {text-decoration:none;} this line's brace)
                        
That's not correct CSS syntax. Correct would be:
If you want to nest CSS rules using the syntax in your question, you can use an alternate stylesheet language that compiles to CSS like LESS or SASS.