diff --git a/static/styles/input_pill.scss b/static/styles/input_pill.scss
index d0a6af85d3..a84eca6e5b 100644
--- a/static/styles/input_pill.scss
+++ b/static/styles/input_pill.scss
@@ -78,7 +78,7 @@
 }
 
 .pill-container .input.shake {
-    animation: shake 0.3s cubic-bezier(.36,.07,.19,.97) both;
+    animation: shake 0.3s cubic-bezier(.36, .07, .19, .97) both;
     transform: translate3d(0, 0, 0);
     backface-visibility: hidden;
     perspective: 1000px;
diff --git a/static/styles/left-sidebar.scss b/static/styles/left-sidebar.scss
index 793c79851f..f53ac38380 100644
--- a/static/styles/left-sidebar.scss
+++ b/static/styles/left-sidebar.scss
@@ -33,7 +33,7 @@
     margin-right: 10px;
 }
 
-.hashtag:empty:after {
+.hashtag:empty::after {
     content: "#";
     font-size: 1.3rem;
     font-weight: 800;
diff --git a/static/styles/media.scss b/static/styles/media.scss
index b6c4779dfe..56e4acaebb 100644
--- a/static/styles/media.scss
+++ b/static/styles/media.scss
@@ -76,7 +76,7 @@
         box-shadow: 0px 0px 5px hsla(0, 0%, 0%, 0.2);
     }
 
-    .nav .dropdown-menu:after {
+    .nav .dropdown-menu::after {
         right: 10px;
     }
 
diff --git a/static/styles/night_mode.scss b/static/styles/night_mode.scss
index e813428a8c..e517d5033c 100644
--- a/static/styles/night_mode.scss
+++ b/static/styles/night_mode.scss
@@ -318,7 +318,7 @@ body.night-mode .mention .messagebox {
 
 body.night-mode .user-mention,
 body.night-mode .user-group-mention {
-    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,hsla(0, 0%, 0%, 0.1)), color-stop(100%,hsla(0, 0%, 0%, 0.0)));
+    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, hsla(0, 0%, 0%, 0.1)), color-stop(100%, hsla(0, 0%, 0%, 0.0)));
     background: -webkit-linear-gradient(top, hsla(0, 0%, 0%, 0.2) 0%, hsla(0, 0%, 0%, 0.1) 100%);
     background: -o-linear-gradient(top, hsla(0, 0%, 0%, 0.2) 0%, hsla(0, 0%, 0%, 0.1) 100%);
     background: -ms-linear-gradient(top, hsla(0, 0%, 0%, 0.2) 0%, hsla(0, 0%, 0%, 0.1) 100%);
@@ -374,7 +374,7 @@ body.night-mode .alert-box .alert.alert-error::before {
 /* Popover: */
 
 body.night-mode .hotspot.overlay .hotspot-popover {
-    border-color: hsla(0, 0%, 0%, 0.2)!important;
+    border-color: hsla(0, 0%, 0%, 0.2) !important;
 
     /* Based on the `.hotspot-popover` shadow in `hotspots.css`, but with a new
     color. */
@@ -456,10 +456,10 @@ body.night-mode .highlight_text_deleted {
     background-color: hsla(7, 54%, 62%, 0.38);
 }
 
-body.night-mode .sub-unsub-message span:before,
-body.night-mode .sub-unsub-message span:after,
-body.night-mode .date_row span:before,
-body.night-mode .date_row span:after {
+body.night-mode .sub-unsub-message span::before,
+body.night-mode .sub-unsub-message span::after,
+body.night-mode .date_row span::before,
+body.night-mode .date_row span::after {
     opacity: 0.2;
 }
 
@@ -476,7 +476,7 @@ body.night-mode .email_tooltip {
     background-color: #404c59;
 }
 
-body.night-mode .email_tooltip:after {
+body.night-mode .email_tooltip::after {
     border-bottom-color: #404c59 !important;
 }
 
diff --git a/static/styles/popovers.scss b/static/styles/popovers.scss
index 4598ebca7f..8a67f4b624 100644
--- a/static/styles/popovers.scss
+++ b/static/styles/popovers.scss
@@ -86,7 +86,7 @@ ul.remind_me_popover .remind_icon {
 
 .user_popover {
     width: 240px;
-    top: 100px!important;
+    top: 100px !important;
 
     margin: -14px;
     padding: 0;
diff --git a/static/styles/portico-signin.scss b/static/styles/portico-signin.scss
index d27f0795a8..3145f007c0 100644
--- a/static/styles/portico-signin.scss
+++ b/static/styles/portico-signin.scss
@@ -316,7 +316,6 @@ html {
 
     border: none;
     color: hsl(0, 44%, 54%);
-
 }
 
 .new-style .right-side .alert {
@@ -575,7 +574,6 @@ html {
     z-index: -1;
 
     border-bottom: 2px solid hsl(0, 0%, 86%);
-
 }
 
 .portico-page .or span {
@@ -620,7 +618,7 @@ button.login-google-button {
     background-image: url(/static/images/landing-page/logos/google-icon.png);
 }
 
-.github-wrapper:before {
+.github-wrapper::before {
     content: "\f09b";
     position: absolute;
 
diff --git a/static/styles/pygments.scss b/static/styles/pygments.scss
index 72a0fbf7ec..e76bbc863e 100644
--- a/static/styles/pygments.scss
+++ b/static/styles/pygments.scss
@@ -13,7 +13,7 @@
     font-style: italic;
 } /* Comment */
 .codehilite .err {
-    border: 1px solid #FF0000;
+    border: 1px solid #ff0000;
 } /* Error */
 .codehilite .k {
     color: hsl(332, 70%, 38%);
@@ -268,7 +268,7 @@ body.night-mode .codehilite .gu {
 }
 
 body.night-mode .codehilite .gt {
-    color: #0040D0;
+    color: #0040d0;
 }
 
 body.night-mode .codehilite .kc {
diff --git a/static/styles/right-sidebar.scss b/static/styles/right-sidebar.scss
index 65c9720955..bc8cb11989 100644
--- a/static/styles/right-sidebar.scss
+++ b/static/styles/right-sidebar.scss
@@ -74,12 +74,12 @@
     background-color: hsl(29, 84%, 51%);
 
     background: -moz-linear-gradient(top, hsla(0, 0%, 100%, 0.0) 50%, hsla(29, 84%, 51%, 1.0) 50%); /* FF3.6+ */
-    background: -webkit-gradient(linear, left top, left bottom, color-stop(50%,hsla(0, 0%, 100%, 0.0)), color-stop(50%,hsla(29, 84%, 51%, 1.0))); /* Chrome,Safari4+ */
+    background: -webkit-gradient(linear, left top, left bottom, color-stop(50%, hsla(0, 0%, 100%, 0.0)), color-stop(50%, hsla(29, 84%, 51%, 1.0))); /* Chrome,Safari4+ */
     background: -webkit-linear-gradient(top, hsla(0, 0%, 100%, 0.0) 50%, hsla(29, 84%, 51%, 1.0) 50%); /* Chrome10+,Safari5.1+ */
     background: -o-linear-gradient(top, hsla(0, 0%, 100%, 0.0) 50%, hsla(29, 84%, 51%, 1.0) 50%); /* Opera 11.10+ */
     background: -ms-linear-gradient(top, hsla(0, 0%, 100%, 0.0) 50%, hsla(29, 84%, 51%, 1.0) 50%); /* IE10+ */
     background: linear-gradient(to bottom, hsla(0, 0%, 100%, 0.0) 50%, hsla(29, 84%, 51%, 1.0) 50%); /* W3C */
-    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#ec7e18',GradientType=0 ); /* IE6-9 */
+    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#ec7e18', GradientType=0 ); /* IE6-9 */
 }
 
 .user-status-indicator {
diff --git a/static/styles/settings.scss b/static/styles/settings.scss
index 58dab171f6..2d2bf9ef8a 100644
--- a/static/styles/settings.scss
+++ b/static/styles/settings.scss
@@ -365,7 +365,7 @@ input[type=checkbox] + .inline-block {
 
 #settings_page .icon-button {
     border-radius: 5px;
-    border: 1px solid hsl(0,0%,80%);
+    border: 1px solid hsl(0, 0%, 80%);
     font-size: 14px;
     padding: 3px 14px 4px 11px;
     text-decoration: none;
@@ -474,9 +474,9 @@ input[type=checkbox].inline-block {
 }
 
 .remove-attachment {
-    margin-right: 5px       !important;
-    font-size: 1.1em        !important;
-    padding-left: 0px       !important;
+    margin-right: 5px !important;
+    font-size: 1.1em !important;
+    padding-left: 0px !important;
 }
 
 #download_attachment {
@@ -1255,7 +1255,7 @@ input[type=checkbox].inline-block {
     transform: translateY(-50%);
 }
 
-#settings_page .table-striped thead th.active:after {
+#settings_page .table-striped thead th.active::after {
     content: " \f0d8";
     white-space: pre;
     display: inline-block;
@@ -1266,7 +1266,7 @@ input[type=checkbox].inline-block {
     -moz-osx-font-smoothing: grayscale;
 }
 
-#settings_page .table-striped thead th.active.descend:after {
+#settings_page .table-striped thead th.active.descend::after {
     content: " \f0d7";
 }
 
diff --git a/static/styles/stats.scss b/static/styles/stats.scss
index bf97330988..163ce20958 100644
--- a/static/styles/stats.scss
+++ b/static/styles/stats.scss
@@ -196,7 +196,7 @@ hr {
     }
 }
 
-.spinner:before {
+.spinner::before {
     content: '';
     box-sizing: border-box;
     position: absolute;
diff --git a/static/styles/subscriptions.scss b/static/styles/subscriptions.scss
index 049e489852..d7b6f8ec0e 100644
--- a/static/styles/subscriptions.scss
+++ b/static/styles/subscriptions.scss
@@ -496,11 +496,11 @@ form#add_new_subscription {
     border-bottom: 1px solid hsl(0, 0%, 86%);
 }
 
-.subscriptions-container .display-type.preview:after {
+.subscriptions-container .display-type.preview::after {
     content: "Preview";
 }
 
-.subscriptions-container .display-type.preferences:after {
+.subscriptions-container .display-type.preferences::after {
     content: "Preferences";
 }
 
@@ -721,8 +721,8 @@ form#add_new_subscription {
     line-height: 1.5;
 }
 
-#subscription_overlay .stream-description .stream-description-editable:empty:after,
-.stream-row .sub-info-box .description:empty:after {
+#subscription_overlay .stream-description .stream-description-editable:empty::after,
+.stream-row .sub-info-box .description:empty::after {
     content: attr(data-no-description);
     font-style: italic;
     color: hsl(0, 0%, 66%);
@@ -865,7 +865,7 @@ form#add_new_subscription {
     transition: all 0.3s ease;
 }
 
-#subscription_overlay .editable:empty:before {
+#subscription_overlay .editable:empty::before {
     content: "\f040";
     font-family: "FontAwesome";
     font-size: 0.8rem;
diff --git a/static/styles/zulip.scss b/static/styles/zulip.scss
index 0bb04aa6f6..b24843afda 100644
--- a/static/styles/zulip.scss
+++ b/static/styles/zulip.scss
@@ -628,11 +628,11 @@ td.pointer {
     @include prefixed-user-select(none);
 }
 
-.include-sender .message_edit_notice:before {
+.include-sender .message_edit_notice::before {
     content: "(";
 }
 
-.include-sender .message_edit_notice:after {
+.include-sender .message_edit_notice::after {
     content: ")";
 }
 
@@ -774,7 +774,7 @@ td.pointer {
     text-decoration: none;
 }
 
-.stream_label:after {
+.stream_label::after {
     left: 100%;
     top: 50%;
     content: " ";
@@ -790,7 +790,7 @@ td.pointer {
     -moz-transform: scale(.9999);
 }
 
-.stream_label:before {
+.stream_label::before {
     left: 100%;
     top: 50%;
     content: " ";
@@ -861,7 +861,8 @@ td.pointer {
 
 .summary_row.last_message .message_header {
     border-bottom-right-radius: 3px;
-    box-shadow: inset 0px 2px 1px -2px hsl(0, 0%, 20%),
+    box-shadow:
+        inset 0px 2px 1px -2px hsl(0, 0%, 20%),
         inset -2px 0px 1px -2px hsl(0, 0%, 20%),
         inset 0px -2px 1px -2px hsl(0, 0%, 20%);
 }
@@ -928,7 +929,6 @@ td.pointer {
 @-ms-keyframes rotate {
     from {
         -ms-transform: rotate(0deg);
-
     }
 
     to {
@@ -1102,7 +1102,8 @@ td.pointer {
 }
 
 .selected_message .messagebox-content {
-    box-shadow: inset 0px 0px 0px 2px hsl(215, 47%, 50%),
+    box-shadow:
+        inset 0px 0px 0px 2px hsl(215, 47%, 50%),
         -1px -1px 0px 0px hsl(215, 47%, 50%),
         1px 1px 0px 0px hsl(215, 47%, 50%),
         -1px 1px 0px 0px hsl(215, 47%, 50%),
@@ -1333,7 +1334,7 @@ div.focused_table {
 
 .message_edit_content {
     line-height: 18px;
-    resize: vertical!important;
+    resize: vertical !important;
     max-height: 24em;
 }
 
@@ -1599,7 +1600,7 @@ blockquote p {
     color: hsl(0, 0%, 100%);
 }
 
-#tab_list li.inactive:before {
+#tab_list li.inactive::before {
     left: 100%;
     top: 50%;
     content: " ";
@@ -1771,7 +1772,7 @@ blockquote p {
     text-align: center;
 }
 
-.nav .dropdown-menu:after {
+.nav .dropdown-menu::after {
     position: absolute;
     width: 0px;
     height: 0px;
@@ -1830,7 +1831,6 @@ nav .column-left .nav-logo {
     margin-top: 8px;
     width: 25px;
     height: 25px;
-
 }
 
 nav .column-left .company-name {
@@ -2611,10 +2611,10 @@ div.topic_edit_spinner .loading_indicator_spinner {
     text-transform: none;
 }
 
-.sub-unsub-message span:before,
-.sub-unsub-message span:after,
-.date_row span:before,
-.date_row span:after {
+.sub-unsub-message span::before,
+.sub-unsub-message span::after,
+.date_row span::before,
+.date_row span::after {
     display: inline-block;
     position: relative;
     content: " ";
@@ -2625,14 +2625,14 @@ div.topic_edit_spinner .loading_indicator_spinner {
     border-bottom: 1px solid #fff;
 }
 
-.sub-unsub-message span:before,
-.date_row span:before {
+.sub-unsub-message span::before,
+.date_row span::before {
     right: 0.5em;
     margin-left: -50%;
 }
 
-.sub-unsub-message span:after,
-.date_row span:after {
+.sub-unsub-message span::after,
+.date_row span::after {
     left: 0.5em;
     margin-right: -50%;
 }
@@ -2714,7 +2714,7 @@ div.topic_edit_spinner .loading_indicator_spinner {
     margin-left: 2px;
     white-space: nowrap;
     background: -moz-linear-gradient(top, hsla(0, 0%, 0%, 0.1) 0%, hsla(0, 0%, 0%, 0.0) 100%);
-    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,hsla(0, 0%, 0%, 0.1)), color-stop(100%,hsla(0, 0%, 0%, 0.0)));
+    background: -webkit-gradient(linear, left top, left bottom, color-stop(0%, hsla(0, 0%, 0%, 0.1)), color-stop(100%, hsla(0, 0%, 0%, 0.0)));
     background: -webkit-linear-gradient(top, hsla(0, 0%, 0%, 0.1) 0%, hsla(0, 0%, 0%, 0.0) 100%);
     background: -o-linear-gradient(top, hsla(0, 0%, 0%, 0.1) 0%, hsla(0, 0%, 0%, 0.0) 100%);
     background: -ms-linear-gradient(top, hsla(0, 0%, 0%, 0.1) 0%, hsla(0, 0%, 0%, 0.0) 100%);
diff --git a/templates/zerver/emails/email.css b/templates/zerver/emails/email.css
index 9e4403143a..b1a8174768 100644
--- a/templates/zerver/emails/email.css
+++ b/templates/zerver/emails/email.css
@@ -167,7 +167,7 @@ a.button:hover {
 
 .illustration {
     pointer-events: none;
-    cursor: default!important;
+    cursor: default !important;
     z-index: 100;
 }