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Why will some pdfs open but others won't?


When I open pdfs in my browser they should open as tabs but some don't. These are not different types - I'm currently doing GCSEs and on one webpage there will be, for example, links to 3 mark schemes, all the same format, same server etc. - but only 1 will open, and it will open immediately and without problems. The other two will come up with the grey screen and bar at the top which should be for pdfs, but nothing happens if I try to use this bar to download the pdfs etc. and the loading bar in the centre of the page does not load. If I refresh a lot, one of these may then open. Some will not open after being left for hours or refreshed many times, however. All of the pdfs open on other computers. Why is this and how can I solve it? Thanks for any suggestions. Btw, as far as I can see all the pdf extensions etc. are downloaded and installed.

Additional System Details

Installed Plug-ins

  • Google Update
  • Shockwave Flash 11.7 r700
  • Next Generation Java Plug-in 10.21.2 for Mozilla browsers
  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • iTunes Detector Plug-in
  • Picasa plugin
  • GEPlugin
  • Adobe PDF Plug-In For Firefox and Netscape 11.0.02
  • 5.1.20125.0
  • The QuickTime Plugin allows you to view a wide variety of multimedia content in Web pages. For more information, visit the QuickTime Web site.
  • Adobe Shockwave for Director Netscape plug-in, version
  • Adobe Shockwave for Director Netscape plug-in, version
  • Autograph Plugin for Firefox


  • Firefox 20.0.1
  • User Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:20.0) Gecko/20100101 Firefox/20.0
  • Support URL: http://support.mozilla.org/1/firefox/20.0.1/WINNT/en-US/


  • Troubleshooter 1.1a (troubleshooter@mozilla.org)
  • Xmarks 4.2.1 (foxmarks@kei.com)
  • Anti-Banner (anti_banner@kaspersky.com) (Inactive)
  • Content Blocker (content_blocker@kaspersky.com) (Inactive)
  • Kaspersky URL Advisor (url_advisor@kaspersky.com) (Inactive)
  • Nectar Search Toolbar 1.300.436 ({841468a1-d7f4-4bd3-84e6-bb0f13a06c64}) (Inactive)
  • Safe Money (online_banking@kaspersky.com) (Inactive)
  • Virtual Keyboard (virtual_keyboard@kaspersky.com) (Inactive)


  • incrementalGCEnabled: True


  • adapterDescription: Mobile Intel(R) 4 Series Express Chipset Family (Microsoft Corporation - WDDM 1.1)
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  • adapterVendorID2:
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  • driverDate: 3-24-2012
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  • numTotalWindows: 2
  • webglRenderer: Google Inc. -- ANGLE (Mobile Intel(R) 4 Series Express Chipset Family (Microsoft Corporation - WDDM 1.1))
  • windowLayerManagerType: Direct3D 10

Modified Preferences

  • accessibility.typeaheadfind.flashBar: 0
  • browser.cache.disk.capacity: 358400
  • browser.cache.disk.smart_size.first_run: False
  • browser.cache.disk.smart_size.use_old_max: False
  • browser.cache.disk.smart_size_cached_value: 358400
  • browser.places.smartBookmarksVersion: 4
  • browser.search.useDBForOrder: True
  • browser.startup.homepage: http://www.nectar.com
  • browser.startup.homepage_override.buildID: 20130409194949
  • browser.startup.homepage_override.mstone: 20.0.1
  • dom.mozApps.used: True
  • dom.w3c_touch_events.expose: False
  • extensions.lastAppVersion: 20.0.1
  • gfx.direct3d.checkDX10: False
  • keyword.URL: https://www.google.co.uk/search?q=
  • network.cookie.prefsMigrated: True
  • places.database.lastMaintenance: 1369941253
  • places.history.expiration.transient_current_max_pages: 104858
  • plugin.disable_full_page_plugin_for_types: application/pdf
  • privacy.sanitize.migrateFx3Prefs: True


  • User JS: No
  • Accessibility: No
Ed 95 solutions 596 answers

I noticed you are using Firefox v20. Could you please update your browser to v21 and see if that solves the issue?

Question owner

How can I do this? It says to go onto 'About Firefox' and it will find updates but it doesn't even look for any when I do that.

Ed 95 solutions 596 answers

I've attached an image. Are you not seeing the spinning circle and the 'Checking for updates...' message?

In that case you can download Firefox 21.0 from here:


Install the file and it will replace your current version. Bookmarks, history etc will be saved.

Question owner

It doesn't check for updates - thanks for the link, am downloading now.

Question owner

Have just updated, the pdfs still seem to be an issue :/

  • Top 10 Contributor
  • Moderator
10783 solutions 97054 answers

You can try to increase the dom.workers.maxPerDomain pref to a higher value.