这有一个不错的html 学习资源：https://www.w3schools.com/tags/tag_hn.asp

简单了解html 基础元素

有以下内容：

使用这些代码时，shiny 将会将它们转换为对应的html 代码：

> h1("My title")
<h1>My title</h1>

我们除了可以直接在fluidPage 函数内使用，也可以将他们作为参数传递给titlePanel, sidebarPanel, or mainPanel：

ui <- fluidPage(
  h1("My title"),
  titlePanel(h2("My title")),
  sidebarLayout(
    sidebarPanel(h3("My title")),
    mainPanel("main panel")
  )
)

感受以下各级标题的魅力吧：

ui <- fluidPage(
  titlePanel("My Shiny App"),
  sidebarLayout(
    sidebarPanel(),
    mainPanel(
      h1("First level title"),
      h2("Second level title"),
      h3("Third level title"),
      h4("Fourth level title"),
      h5("Fifth level title"),
      h6("Sixth level title")
    )
  )
)

我们还可以通过align参数调整文本的位置：

ui <- fluidPage(
  titlePanel("My Star Wars App"),
  sidebarLayout(
    sidebarPanel(),
    mainPanel(
      h6("Episode IV", align = "center"),
      h6("A NEW HOPE", align = "center"),
      h5("It is a period of civil war.", align = "center"),
      h4("Rebel spaceships, striking", align = "center"),
      h3("from a hidden base, have won", align = "center"),
      h2("their first victory against the", align = "center"),
      h1("evil Galactic Empire.")
    )
  )
)

格式化文本

我们可以通过下面的格式化文本例子，一窥html 语法的各个元素：

ui <- fluidPage(
  titlePanel("My Shiny App"),
  sidebarLayout(
    sidebarPanel(),
    mainPanel(
      p("p creates a paragraph of text."), 
      p("A new p() command starts a new paragraph. Supply a style attribute to change the format of the entire paragraph.", style = "font-family: 'times'; font-si16pt"),
      strong("strong() makes bold text."), 
      em("em() creates italicized (i.e, emphasized) text."),
      br(), # 空格一段
      code("code displays your text similar to computer code"),
      # 可以给一段内容分配相同的风格
      div("div creates segments of text with a similar style. This division of text is all blue because I passed the argument 'style = color:blue' to div", style = "color:blue"),
      br(),
      p("span does the same thing as div, but it works with",
        span("groups of words", style = "color:blue"), # 类似div 但可以在元素内部进行调整
        "that appear inside a paragraph.")
    )
  )
)

图片

如果想要将图片添加到shiny中，我们需要将图片保存在：

接着使用函数img：

ui <- fluidPage(
  titlePanel("My Shiny App"),
  sidebarLayout(
    sidebarPanel("empty panel"),
    mainPanel(
      p("Here is one of my cute photo."), 
      img(src = "cute.png", height = 500, width = 400)
    )
  )
)

这里还有进阶内容：https://shiny.rstudio.com/articles/html-tags.html