diff --git a/NEWS.md b/NEWS.md
index ec55e63d8..8c5593baf 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -40,6 +40,10 @@
 
 - Improve common chunk detection, output `na_group` and `row_in_group` when there are missing values.
 
+# Changes in version 2025.10.6 (PR#246)
+
+- Added validation for selector names to prevent browser rendering failures. Selector names (from data values used in `clickSelects` and `showSelected`) cannot contain CSS special characters like `#`, `@`, `!`, `$`, etc., as these interfere with JavaScript DOM selectors and cause blank visualizations in the browser. The compiler now stops with a clear error message identifying problematic selector names, helping users fix data issues before attempting to render.
+
 # Changes in version 2025.10.3 (PR#240)
 
 - `guide_legend(override.aes)` works in a plot with both color and fill legends.
diff --git a/R/z_animint.R b/R/z_animint.R
index 3beb7dd7c..c50bfee02 100644
--- a/R/z_animint.R
+++ b/R/z_animint.R
@@ -438,6 +438,9 @@ animint2dir <- function
   ## For a static data viz with no interactive aes, no need to check
   ## for trivial showSelected variables with only 1 level.
   checkSingleShowSelectedValue(meta$selectors)
+  
+  ## Check selector names for CSS compatibility (no special characters like #)
+  checkSelectorNames(meta$selectors)
 
   ## Go through options and add to the list.
   for(v.name in names(meta$duration)){
diff --git a/R/z_animintHelpers.R b/R/z_animintHelpers.R
index f36864547..97cce5a7f 100644
--- a/R/z_animintHelpers.R
+++ b/R/z_animintHelpers.R
@@ -607,6 +607,22 @@ checkSingleShowSelectedValue <- function(selectors){
 }
 
 
+#' Validate selector names for CSS compatibility
+#' @param selectors selectors to validate
+#' @return \code{NULL}. Throws error if invalid characters found.
+checkSelectorNames <- function(selectors){
+  selector.names <- names(selectors)
+  ## Characters that are invalid in CSS selectors and cause issues in browser
+  ## ] must be first in character class, [ can be anywhere after
+  invalid.pattern <- "[][#!@$%^&*=|/'\"`?<>()\\\\]"
+  has.invalid <- grepl(invalid.pattern, selector.names)
+  if(any(has.invalid)){
+    invalid.names <- selector.names[has.invalid]
+    stop(sprintf("Invalid character(s) in selector name(s).\nSelector names cannot contain special characters that interfere with CSS selectors.\nThe following selector(s) contain invalid characters:\n%s\n\nPlease remove or replace these characters in your variable names.", paste("-", invalid.names, collapse="\n")))
+  }
+}
+
+
 #' Set plot width and height for all plots
 #' @param meta meta object with all information
 #' @param AllPlotsInfo plot info list
diff --git a/tests/testthat/test-compiler-invalid-selector-characters.R b/tests/testthat/test-compiler-invalid-selector-characters.R
new file mode 100644
index 000000000..29a5594de
--- /dev/null
+++ b/tests/testthat/test-compiler-invalid-selector-characters.R
@@ -0,0 +1,130 @@
+context("Invalid selector character validation")
+
+# Test that selector names with special characters cause errors
+# Note: Selector names come from the VALUES in the data when using .variable/.value pattern
+test_that("selector name with # causes error in clickSelects", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(Sepal.Length, Petal.Length),
+        data = data.frame(
+          Sepal.Length = 1:10,
+          Petal.Length = rnorm(10),
+          regularization = "# nearest neighbors",  # This VALUE becomes the selector name
+          parameter = 1:10
+        ),
+        clickSelects = c(regularization = "parameter")
+      )
+  )
+  expect_error(
+    animint2dir(viz, open.browser = FALSE),
+    "Invalid character(s) in selector name(s).
+Selector names cannot contain special characters that interfere with CSS selectors.
+The following selector(s) contain invalid characters:
+- # nearest neighbors
+
+Please remove or replace these characters in your variable names.",
+    fixed = TRUE
+  )
+})
+
+test_that("selector name with @ causes error in clickSelects", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(Sepal.Length, Petal.Length),
+        data = data.frame(
+          Sepal.Length = 1:10,
+          Petal.Length = rnorm(10),
+          regularization = "model@version1",  # This VALUE becomes selector name
+          parameter = 1:10
+        ),
+        clickSelects = c(regularization = "parameter")
+      )
+  )
+  expect_error(
+    animint2dir(viz, open.browser = FALSE),
+    "Invalid character(s) in selector name(s).
+Selector names cannot contain special characters that interfere with CSS selectors.
+The following selector(s) contain invalid characters:
+- model@version1
+
+Please remove or replace these characters in your variable names.",
+    fixed = TRUE
+  )
+})
+
+test_that("selector name with ! causes error", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(x=1:10, y=rnorm(10)),
+        data = data.frame(
+          model = "model!important",
+          parameter = 1:10
+        ),
+        clickSelects = c(model = "parameter")
+      )
+  )
+  expect_error(
+    animint2dir(viz, open.browser = FALSE),
+    "Invalid character(s) in selector name(s).
+Selector names cannot contain special characters that interfere with CSS selectors.
+The following selector(s) contain invalid characters:
+- model!important
+
+Please remove or replace these characters in your variable names.",
+    fixed = TRUE
+  )
+})
+
+test_that("valid selector names work with clickSelects", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(x=1:10, y=rnorm(10)),
+        data = data.frame(
+          regularization = "polynomial_degree",  # Valid name
+          parameter = 0:9
+        ),
+        clickSelects = c(regularization = "parameter")
+      )
+  )
+  info <- animint2dir(viz, open.browser = FALSE)
+  expect_true(TRUE, info = "Valid selector names should not cause errors")
+})
+
+test_that("selector names with spaces work", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(x=1:10, y=rnorm(10)),
+        data = data.frame(
+          regularization = "nearest neighbors",  # spaces are OK
+          parameter = 1:10
+        ),
+        clickSelects = c(regularization = "parameter")
+      )
+  )
+  info <- animint2dir(viz, open.browser = FALSE)
+  expect_true(TRUE, info = "Selector names with spaces should work")
+})
+
+test_that("multiple values with invalid characters all reported", {
+  viz <- list(
+    plot1 = ggplot() +
+      geom_point(
+        aes(x=1:10, y=rnorm(10)),
+        data = data.frame(
+          regularization = rep(c("#bad", "!worse"), 5),  # Both have invalid chars
+          parameter = 1:10
+        ),
+        clickSelects = c(regularization = "parameter")
+      )
+  )
+  expect_error(
+    animint2dir(viz, open.browser = FALSE),
+    "Invalid character(s) in selector name(s).\nSelector names cannot contain special characters that interfere with CSS selectors.\nThe following selector(s) contain invalid characters:\n- #bad\n- !worse\n\nPlease remove or replace these characters in your variable names.",
+    fixed = TRUE
+  )
+})