xpath - While clicking on the View Button in dialogue box it's not Finding element in selenium webdriver -

enter image description hereenter image description here****this page developed in c#(asp.net)*****

[enter image description here][2]on page 1 dialog box's close button working , other dialog box's close button not working , vice versa.

//closing training view button
driver.findelement(by.xpath("/html/body/div[2]/div[3]/div/button/span")).click(); thread.sleep(2000);

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error in eclipse::

exception in thread "main" org.openqa.selenium.elementnotvisibleexception: element not visible , may not interacted command duration or timeout: 10.05 seconds build info: version: '2.53.0', revision: '35ae25b', time: '2016-03-15 16:57:40' system info: host: 'bishnuprasad', ip: '172.16.12.108', os.name: 'windows 7', os.arch: 'x86', os.version: '6.1', java.version: '1.7.0_45' session id: e35dda6a-1c9b-4345-8412-c225a0ebeba3 driver info: org.openqa.selenium.firefox.firefoxdriver capabilities [{platform=windows, acceptsslcerts=true, javascriptenabled=true, cssselectorsenabled=true, databaseenabled=true, browsername=firefox, handlesalerts=true, nativeevents=false, webstorageenabled=true, rotatable=false, locationcontextenabled=true, applicationcacheenabled=true, takesscreenshot=true, version=43.0.1}] @ sun.reflect.nativeconstructoraccessorimpl.newinstance0(native method) @ sun.reflect.nativeconstructoraccessorimpl.newinstance(nativeconstructoraccessorimpl.java:57) @ sun.reflect.delegatingconstructoraccessorimpl.newinstance(delegatingconstructoraccessorimpl.java:45) @ java.lang.reflect.constructor.newinstance(constructor.java:526) @ org.openqa.selenium.remote.errorhandler.createthrowable(errorhandler.java:206) @ org.openqa.selenium.remote.errorhandler.throwifresponsefailed(errorhandler.java:158) @ org.openqa.selenium.remote.remotewebdriver.execute(remotewebdriver.java:678) @ org.openqa.selenium.remote.remotewebelement.execute(remotewebelement.java:327) @ org.openqa.selenium.remote.remotewebelement.click(remotewebelement.java:85) @ arms.amiri.main(amiri.java:93) caused by: org.openqa.selenium.elementnotvisibleexception: element not visible , may not interacted build info: version: '2.53.0', revision: '35ae25b', time: '2016-03-15 16:57:40' system info: host: 'bishnuprasad', ip: '172.16.12.108', os.name: 'windows 7', os.arch: 'x86', os.version: '6.1', java.version: '1.7.0_45' driver info: driver.version: unknown @ .fxdriver.preconditions.visible(file:///c:/users/bishnu/appdata/local/temp/anonymous5983937291135292550webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:10092) @ .delayedcommand.prototype.checkpreconditions_(file:///c:/users/bishnu/appdata/local/temp/anonymous5983937291135292550webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:12644) @ .delayedcommand.prototype.executeinternal_/h(file:///c:/users/bishnu/appdata/local/temp/anonymous5983937291135292550webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:12661) @ .fxdriver.timer.prototype.settimeout/<.notify(file:///c:/users/bishnu/appdata/local/temp/anonymous5983937291135292550webdriver-profile/extensions/fxdriver@googlecode.com/components/command-processor.js:625)

possible have button hidden , first button found one. can try simple css this:

div[style*=block] button.ui-widget.ui-dialog-titlebar-close