document.getElementById("bla").style.width = "calc(100% - 15px)";
document.querySelector(".current").onclick = go();document.querySelector(".current").onclick = go;
.main {
position: relative;
}
.main нужно задать position: relative; для корректного отображения блока .go
Adjacent sibling selectors
Adjacent sibling selectors have the following syntax: E1 + E2, where E2 is the subject of the selector. The selector matches if E1 and E2 share the same parent in the document tree and E1 immediately precedes E2, ignoring non-element nodes (such as text nodes and comments).