How large is the usable area in iPad Safari

If you want to know screen aspects you could check iPad Peek and load a site like NYTIMES. this gives the exact usable screen dimensions for the iPad.

Hope this helps

So - on my ipad (ipad1, ios 5.1.1) I got slightly different numbers than above. Probably because the tab and bookmarks bars are showing.
My values:

    portrait  : 768  x 900
    landscape : 1024 x 644

So I wrote a javascript bookmarklet to get a proof positive result. You can email this to yourself, goto "about:blank" in safari, create a bookmark, edit it and cut/paste this code out of email :)

When you get the bookmarklet running re-size the div until it matches the window and tada..

<pre><code>
javascript:( function(){
  "use strict";
  var bmIdVal = "ios_screen_res_test_bookmarklet";
  var bmDivSize = {
    w : 320,
    h : 240 
  };

  var vpMeta1 = document.createElement('meta');
  vpMeta1.setAttribute("name","viewport");
  vpMeta1.setAttribute("content",'initial-scale=1.0, user-scalable=no');
  document.head.appendChild(vpMeta1);

  function updateStatus(){
    statusDiv.innerHTML = "div is " + bmDivSize.w + ',' + bmDivSize.h + 
      " doc body says: " + document.body.clientWidth + "," + 
      document.body.clientHeight;
  }

  function resizeBmDiv(wPx,hPx){
    bmDivSize.w += wPx;
    bmDivSize.h += hPx;
    bmDiv.style.width=bmDivSize.w + "px";
    bmDiv.style.height=bmDivSize.h + "px";
    updateStatus();
  }

  var prevBmDiv = document.getElementById(bmIdVal); 
  if( prevBmDiv != null){
    document.body.removeChild(prevBmDiv);
  }
  var bmDiv = document.createElement("div");
  bmDiv.setAttribute("id",bmIdVal);
  bmDiv.style.cssText = 
    "position:absolute;left:0px;top:0px;background-color: #0066FF";
  bmDiv.style.width=bmDivSize.w + "px";
  bmDiv.style.height=bmDivSize.h + "px";

  var sizerB_w1 = document.createElement("button");
  sizerB_w1.style.cssText = "width:64px;height:64px";
  sizerB_w1.innerHTML="w+1";
  sizerB_w1.onclick = function(evt){
    resizeBmDiv(1,0);
  };
  var sizerB_w100 = document.createElement("button");
  sizerB_w100.style.cssText = "width:64px;height:64px";
  sizerB_w100.innerHTML="w+100";
  sizerB_w100.onclick = function(evt){
    resizeBmDiv(100,0);
  };
  var sizerB_h1 = document.createElement("button");
  sizerB_h1.style.cssText = "width:64px;height:64px";
  sizerB_h1.innerHTML="h+1";
  sizerB_h1.onclick = function(evt){
    resizeBmDiv(0,1);
  };
  var sizerB_h100 = document.createElement("button");
  sizerB_h100.style.cssText = "width:64px;height:64px";
  sizerB_h100.innerHTML="h+100";
  sizerB_h100.onclick = function(evt){
    resizeBmDiv(0,100);
  };

  var sizerDiv = document.createElement('div');
  sizerDiv.appendChild(sizerB_w1);
  sizerDiv.appendChild(sizerB_w100);
  sizerDiv.appendChild(sizerB_h1);
  sizerDiv.appendChild(sizerB_h100);

  var sizerB_wm1 = document.createElement("button");
  sizerB_wm1.style.cssText = "width:64px;height:64px";
  sizerB_wm1.innerHTML="w-1";
  sizerB_wm1.onclick = function(evt){
    resizeBmDiv(-1,0);
  };
  var sizerB_wm100 = document.createElement("button");
  sizerB_wm100.style.cssText = "width:64px;height:64px";
  sizerB_wm100.innerHTML="w-100";
  sizerB_wm100.onclick = function(evt){
    resizeBmDiv(-100,0);
  };
  var sizerB_hm1 = document.createElement("button");
  sizerB_hm1.style.cssText = "width:64px;height:64px";
  sizerB_hm1.innerHTML="h-1";
  sizerB_hm1.onclick = function(evt){
    resizeBmDiv(0,-1);
  };
  var sizerB_hm100 = document.createElement("button");
  sizerB_hm100.style.cssText = "width:64px;height:64px";
  sizerB_hm100.innerHTML="h-100";
  sizerB_hm100.onclick = function(evt){
    resizeBmDiv(0,-100);
  };

  var sizerMDiv = document.createElement('div');
  sizerMDiv.appendChild(sizerB_wm1);
  sizerMDiv.appendChild(sizerB_wm100);
  sizerMDiv.appendChild(sizerB_hm1);
  sizerMDiv.appendChild(sizerB_hm100);

  var statusDiv = document.createElement('div');
  statusDiv.style.cssText = "color:white;";

  bmDiv.appendChild(statusDiv);
  bmDiv.appendChild(sizerDiv);
  bmDiv.appendChild(sizerMDiv);
  document.body.appendChild(bmDiv);
  updateStatus();  
})();
</code></pre>

You should just follow TN2262 and write dimension-invariant code.

In case you need a logical pixel size, document.body.client[Width|Height] is always 980×1208.

---

In terms of absolute pixels you can use, the navigation bar of Mobile Safari takes up roughly 78px, so in portrait orientation it is 768×946, and in landscape it is 1024×690.

There can be a keyboard (308px in height in portrait, 397px in landscape) as well.

Update: The above absolute numbers are correct only for iOS 4.x or before. In iOS 5.x Apple introduced the tab bar which increases the height of navigation bar + status bar to 96px. Actually, even before iOS 5.x, the presence of the bookmark bar can affect the viewport as well.