diff --git a/Themes/default/css/calendar.css b/Themes/default/css/calendar.css
index 45053d1a74..a4eaee0464 100644
--- a/Themes/default/css/calendar.css
+++ b/Themes/default/css/calendar.css
@@ -21,7 +21,7 @@ td.days:hover {
 }
 #month_grid {
 	width: 214px;
-	float: left;
+	float: inline-start;
 	text-align: center;
 	overflow: hidden;
 	margin-right: 10px;
diff --git a/Themes/default/css/calendar.rtl.css b/Themes/default/css/calendar.rtl.css
index 976b0be219..692550c25a 100644
--- a/Themes/default/css/calendar.rtl.css
+++ b/Themes/default/css/calendar.rtl.css
@@ -4,7 +4,6 @@
 	margin: 0 0 0 2px;
 }
 #month_grid {
-	float: right;
 	margin: 0 0 0 1%;
 }
 #main_grid table.weeklist td.windowbg {
diff --git a/Themes/default/css/index.css b/Themes/default/css/index.css
index 2a60a91631..3cc722d75b 100644
--- a/Themes/default/css/index.css
+++ b/Themes/default/css/index.css
@@ -1255,7 +1255,7 @@ html[lang="el-GR"] .inline_mod_check {
 	height: 18px;
 	width: 18px;
 	margin: 2px 5px 0 0;
-	float: left;
+	float: inline-start;
 }
 #pm_menu_top .main_icons,
 #alerts_menu_top .main_icons {
@@ -1540,7 +1540,7 @@ ul li.greeting {
 }
 .mark_read {
 	margin: -5px 0 16px 0;
-	float: right;
+	float: inline-end;
 }
 .mark_read .buttonlist {
 	margin: 0;
@@ -1862,7 +1862,7 @@ fieldset.merge_options {
 	padding: 1px;
 }
 .login dt {
-	float: left;
+	float: inline-start;
 	clear: both;
 	text-align: right;
 	font-weight: bold;
@@ -1898,7 +1898,7 @@ dl.register_form {
 }
 dl.register_form dt {
 	font-weight: normal;
-	float: left;
+	float: inline-start;
 	clear: both;
 	width: 50%;
 	margin: 6px 0 0 0;
@@ -2386,7 +2386,7 @@ a.main_icons.feed::before {
 .errorbox p.alert {
 	padding: 0;
 	margin: 0 4px 0 0;
-	float: left;
+	float: inline-start;
 	width: 12px;
 	font-size: 1.5em;
 }
@@ -2505,14 +2505,14 @@ dl {
 
 /* View posts */
 .topic .time {
-	float: right;
+	float: inline-end;
 }
 .counter {
 	padding: 5px 6px 1px 2px;
 	font-size: 2.2em;
 	font-weight: bold;
 	color: var(--counter-color);
-	float: left;
+	float: inline-start;
 }
 .topic_details {
 	padding: 0 4px 4px 4px;
@@ -2613,7 +2613,7 @@ dl {
 /* Pick theme */
 #pick_theme {
 	width: 100%;
-	float: left;
+	float: inline-start;
 }
 #pick_theme .selected {
 	background: var(--picktheme-selected-bg);
@@ -2628,7 +2628,7 @@ dl {
 }
 dl.stats dt {
 	width: 50%;
-	float: left;
+	float: inline-start;
 	margin: 0 0 4px 0;
 	line-height: 1.5em;
 	clear: both;
@@ -2724,7 +2724,7 @@ dl.addrules dt.floatleft {
 	clear: both;
 }
 #to_item_list_container div, #bcc_item_list_container div {
-	float: left;
+	float: inline-start;
 	margin-right: 10px;
 }
 .unread_pm {
@@ -2830,7 +2830,7 @@ dl.addrules dt.floatleft {
 }
 #advanced_search dd {
 	width: 75%;
-	float: left;
+	float: inline-start;
 	padding: 2px;
 	margin: 0 0 0 6px;
 	text-align: left;
@@ -3087,7 +3087,7 @@ div#manage_boards dl dd textarea[name=desc] {
 	margin-bottom: 15px;
 }
 h3 .collapse {
-	float: right;
+	float: inline-end;
 	margin: 4px 4px 0 0;
 }
 .board_icon a {
@@ -3346,7 +3346,7 @@ span.postby {
 	padding: 4px 0;
 	width: 30%;
 	max-width: 30em;
-	float: left;
+	float: inline-start;
 	clear: left;
 }
 #poll_options dl.options .voted {
@@ -3355,7 +3355,7 @@ span.postby {
 #poll_options dl.options dd {
 	width: 60%;
 	max-width: 45em;
-	float: left;
+	float: inline-start;
 	margin: 0 0 4px 0;
 	text-align: right;
 }
@@ -3414,7 +3414,7 @@ div#pollmoderation {
 }
 /* poster details and list of items */
 .poster {
-	float: left;
+	float: inline-start;
 	/* Don't set this in em.It will eat too much space if people need to set large text sizes. */
 	width: 160px;
 	-webkit-hyphens: auto;
@@ -3628,7 +3628,15 @@ form#postmodify .roundframe {
 	padding: 6px;
 	overflow: hidden;
 }
-#post_header dt,
+#post_header dt {
+	float: inline-start;
+	padding: 0;
+	width: 15%;
+	margin: 6px 0 0 0;
+	font-weight: bold;
+}
+/* The event editor is not mirrored for right-to-left yet, so this half of
+   the pair keeps a physical float until it is. */
 #event_options dt {
 	float: left;
 	padding: 0;
@@ -3636,7 +3644,14 @@ form#postmodify .roundframe {
 	margin: 6px 0 0 0;
 	font-weight: bold;
 }
-#post_header dd,
+#post_header dd {
+	float: inline-start;
+	padding: 0;
+	width: 83%;
+	margin: 4px 0;
+}
+/* The event editor is not mirrored for right-to-left yet, so this half of
+   the pair keeps a physical float until it is. */
 #event_options dd {
 	float: left;
 	padding: 0;
@@ -3759,7 +3774,7 @@ form#postmodify .roundframe {
 	float: left;
 }
 #moderationbuttons_strip {
-	float: left;
+	float: inline-start;
 	margin: 4px 0 4px;
 }
 #moderationbuttons ul li {
diff --git a/Themes/default/css/profile.css b/Themes/default/css/profile.css
index 8a43434043..4c89a3c779 100644
--- a/Themes/default/css/profile.css
+++ b/Themes/default/css/profile.css
@@ -14,12 +14,12 @@
 /* The basic user info on the left */
 #basicinfo {
 	width: 20%;
-	float: left;
+	float: inline-start;
 }
 
 #detailedinfo {
 	width: 79.5%;
-	float: right;
+	float: inline-end;
 }
 
 #basicinfo > * {
@@ -47,7 +47,7 @@
 
 #basicinfo .icon_fields li {
 	display: block;
-	float: left;
+	float: inline-start;
 	margin-right: 5px;
 	height: 20px;
 }
@@ -96,7 +96,7 @@
 }
 
 #avatar_server_stored div {
-	float: left;
+	float: inline-start;
 }
 
 #avatar_upload {
@@ -122,7 +122,7 @@
 
 .activity_stats li {
 	width: 4.16%;
-	float: left;
+	float: inline-start;
 	text-align: center;
 }
 
@@ -155,7 +155,7 @@
 .profile_pie {
 	background: url(../images/stats_pie.png);
 	background-size: auto 20px;
-	float: left;
+	float: inline-start;
 	height: 20px;
 	width: 20px;
 	margin: 0 12px 0 0;
diff --git a/Themes/default/css/rtl.css b/Themes/default/css/rtl.css
index 3cd748f49b..d7af7e7eb8 100644
--- a/Themes/default/css/rtl.css
+++ b/Themes/default/css/rtl.css
@@ -106,7 +106,6 @@ img#smflogo {
 
 /* Profile drop it needs reverse on RTL */
 #profile_menu_top > img.avatar {
-	float: right;
 	margin: 2px 0 0 5px;
 }
 #profile_menu .profile_user_info {
@@ -125,29 +124,17 @@ img#smflogo {
 	text-align: left;
 }
 
-
-.mark_read {
-	float: left;
-}
-
 /* Poll results */
 #poll_options dl.options {
 	padding: 1em 2em 1em 2.5em;
 	margin: 0 0 1em 1em;
 }
 #poll_options dl.options dt {
-	float: right;
 	clear: right;
 }
 #poll_options dl.options dd {
-	float: right;
 	text-align: left;
 }
-
-/* poster and postarea + moderation area underneath */
-.poster {
-	float: right;
-}
 .postarea, .moderatorbar {
 	margin: 0 175px 0 0;
 }
@@ -208,10 +195,6 @@ ul.quickbuttons li {
 #forumposts .modified {
 	float: right;
 }
-
-#moderationbuttons_strip {
-	float: right;
-}
 #moderationbuttons_strip ul {
 	margin: 0 0.2em 0 0;
 	padding: 0 1em 0 0;
@@ -229,15 +212,6 @@ ul.quickbuttons li {
 	width: 80px;
 }
 
-/* Styles for edit post section
----------------------------------------------------- */
-#post_header dt {
-	float: right;
-}
-#post_header dd {
-	float: right;
-}
-
 /* Styles for edit poll section.
 ---------------------------------------------------- */
 #edit_poll fieldset input {
@@ -268,7 +242,6 @@ ul.quickbuttons li {
 	padding: 0 0 0 1em;
 }
 #to_item_list_container div, #bcc_item_list_container div {
-	float: right;
 	margin: 0;
 }
 
@@ -276,12 +249,6 @@ ul.quickbuttons li {
 .move_topic {
 	text-align: right;
 }
-
-/* Styles for the login areas.
-------------------------------------------------------- */
-.login dt {
-	float: right;
-}
 .login dd {
 	float: right;
 	text-align: right;
@@ -295,10 +262,6 @@ dl.register_form {
 	clear: left;
 }
 
-dl.register_form dt {
-	float: right;
-}
-
 /* Styles for maintenance mode.
 ------------------------------------------------------- */
 #maintenance_mode img.floatleft {
@@ -338,28 +301,15 @@ div#admin_menu {
 }
 .errorbox p.alert {
 	margin: 0 0 0 4px;
-	float: right;
 }
 .errorbox, .noticebox, .infobox {
 	padding: 7px 35px 7px 10px;
 }
 
-/* Styles for the profile section.
-------------------------------------------------- */
-#basicinfo {
-	float: right;
-}
-#detailedinfo {
-	float: left;
-}
 #basicinfo .icon_fields li {
-	float: right;
 	margin-right: 0;
 	margin-left: 5px;
 }
-#avatar_server_stored div {
-	float: right;
-}
 #detailedinfo dt, #tracking dt {
 	float: right;
 }
@@ -376,9 +326,6 @@ h3.profile_hd {
 #activitytime {
 	clear: right;
 }
-.activity_stats li {
-	float: right;
-}
 .activity_stats li span {
 	border-width: 1px 0 0 1px;
 }
@@ -387,18 +334,11 @@ h3.profile_hd {
 }
 .profile_pie {
 	background-image: url(../images/stats_pie_rtl.png);
-	float: right;
 	margin-right: 0;
 	margin-left: 1em;
 }
-
-/* View posts */
-.topic .time {
-	float: left;
-}
 .counter {
 	padding: 0.2em 0.2em 0.1em 0.5em;
-	float: right;
 }
 
 #ip_list li.header, #ip_list li.ip {
@@ -417,20 +357,10 @@ h3.profile_hd {
 .ignoreboards li {
 	float: right;
 }
-
-#pick_theme {
-	float: right;
-}
 .infolinks {
 	min-width: 95%;
 	float: right;
 }
-
-/* Styles for the statistics center.
-------------------------------------------------- */
-dl.stats dt {
-	float: right;
-}
 dl.stats dd {
 	margin: 0 2% 4px 0;
 }
@@ -458,7 +388,6 @@ tr.windowbg th.stats_month, tr.windowbg td.stats_day {
 	text-align: left;
 }
 #advanced_search dd {
-	float: right;
 	margin: 0 0.5em 0 0;
 	text-align: right;
 }
@@ -534,10 +463,6 @@ ul.moderation_notes li {
 	padding: 4px 4px 4px 0;
 }
 
-h3 .collapse {
-	float: left;
-}
-
 .pages {
 	margin-left: 0;
 	margin-right: 7px;